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rf. 


PREFACE. 


THIS  text-book  on  Chemistry,  intended  for  the  use 
of  colleges  and  schools,  contains  the  outline  of  the 
course  of  Lectures  which  I  give  every  year  in  this 
University. 

I  do  not,  therefore,  present  to  teachers  an  untried 
work.  Its  divisions  and  arrangement  are  the  result 
of  an  experience  of  several  years  ;  an  experience 
which  has  proved  to  me  that  there  is  required  a  text- 
book of  small  size,  so  that  students  can  pass  through 
it  readily  in  the  time  usually  devoted  to  Chemistry. 

Every  instructor  in  this  science  must  have  observ- 
ed that  the  ordinary  "  Treatises"  or  "  Elements"  are 
by  no  means  suited  to  his  wants.  When  they  are 
employed  in  the  class-room,  there  are  large  portions 
which  have  to  be  omitted,  and  other  portions  too 
briefly  explained.  In  fact,  to  study  Chemistry  suc- 
cessfully, the  first  thing  which  is  wanted  is  a  com- 
pendious book,  which  sets  forth  in  plain  language 
the  great  features  of  the  science,  without  perplexing 
the  beginner  with  too  much  detail. 
A2 


M44441 


VI  PREFACE. 

It  will  be  understood,  therefore,  that  this  work, 
with  little  pretensions  to  originality,  except  where 
directly  specified,  occupies  a  different  field  from  that 
of  the  larger  treatises.  It  is  intended  as  a  manual, 
arranged  in  such  divisions  as  practice  has  shown  to 
be  suitable  for  daily  instruction.  It  is  the  exposition 
of  what  I  have  found  to  be  a  satisfactory  method  of 
teaching ;  and  of  its  success  our  annual  examinations 
are  the  best  testimonial. 

The  unsuitableness  of  large  text-books  has  led  to 
many  attempts  to  reduce  their  size  by  abstracts  and 
compendiums  ;  but  the  difficulty  can  never  be  avoid- 
ed by  that  means ;  the  very  structure  of  such  works 
is  faulty.  We  never  want  to  use  all  that  an  author 
knows  or  can  possibly  say  on  the  subject.  It  has 
been  well'  remarked,  that  "  The  greatest  service 
which  can  be  rendered  to  our  science,  is  for  some 
person  who  has  had  the  management  of  large  classes 
for  several  years  to  sit  down  and  write  a  book,  set- 
ting forth  what  he  said  and  what  he  did  every  day  in 
his  Lectures.  That  is  the  thing  we  want." 

While,  therefore,  this  book  is  offered  to  instructors 
as  a  practical  work,  the  object  of  which  is  to  display 
the  leading  features  of  the  science,  I  have  endeavored 
to  make  it  a  representation  of  the  present  state  of 
Chemistry.  In  this  respect  many  of  our  most  popu- 
lar works  are  defective.  Among  them  I  should  not 
know  where  to  turn  for  a  simple  exposition  of  the 


PREFACE.  Vil 


Wave  theory  of  Light  or  of  Ohm's  theory  of  Voltaic 
Currents  ;  yet  the  one  is  the  most  striking  result  of 
physical  research,  and  the  other  is  connected  with 
the  fundamental  facts  of  Electro-chemistry. 

To  the  treatises  of  Hare,  Kane,  Graham,  Gregory, 
Fownes,  Dumas,  and  Millon  I  must  formally  state 
my  obligations.  In  Descriptive  Chemistry  I  have  fol- 
lowed them  closely;  and  in  those  cases  which  are 
much  more  common  than  is  generally  supposed, 
where  there  are  differences  in  the  imputed  proper- 
ties of  bodies,  I  have  consulted,  wherever  I  could, 
either  original  memoirs  or  the  annual  reports  of  Ber- 
zelius.  ^ 

The  number  of  wood-cuts,  representing  experi- 
mental arrangements,  which  have  been  introduced, 
will  give  to  a  beginner  a  clearer  idea  of  the  practical 
part  of  each  Lecture,  and,  in  our  country  colleges, 
may  sometimes  supply  the  place  of  defective  or  in- 
complete apparatus.  To  each  Lecture  is  appended  a 
set  of  questions.  They  enable  a  young  student  more 
quickly  to  apprehend  the  doctrines  which  are  before 
him. 

JOHN  WILLIAM  DRAPER. 

University  of  New  York,  \ 
July  6,  1846.  ) 


CONTENTS. 


Lecture  Page 

I.  Constitution  of  Matter 1 

II.  Constitution  of  Matter  (continued) 6 

III.  Heat 11 

IV.  Expansion  of  Gases  and  Liquids 15 

V.  Expansion  of  Liquids  and  Solids 20 

VL  Expansion  of  Solids 24 

VII.  Capacity  of  Bodies  for  Heat      .        .        .        .  .28 

VIII.  Capacity  for  Heat  and  Latent  Heat          .        .        .        .32 

IX.  Latent  Heat  (continued) 36 

X.  Vaporization 40 

XL  Ebullition 44 

XII.  Vaporization «...    48 

XIII.  Evaporation  and  Interstitial  Radiation     ....    53 

XIV.  Conduction 59 

XV.  Radiation 63 

XVI.  Theory  of  the  Exchanges  of  Heat 67 

XVII.  Nature  of  Light          ....        *        ;.'..!.     .     71 

XVIII.  Constitution  of  the  Solar  Spectrum   .        .       *       »        .    75 
XIX.  Wave  Theory  of  Light      .......    78 

XX.  Wave  Theory  of  Light  (continued)  .        .        .        .        .     82 

XXI.  Wave  Theory  of  Light  (continued)  .        ,        .        .        .86 
XXII.  The  Tithonic  Rays 90 

XXIII.  Theory  of  Ideal  Coloration         ....        .        .        .94 

XXIV.  Electricity 97 

XXV.  Theory  of  Electrical  Induction 101 

XXVT.  Laws  of  the  Distribution  of  Electricity  and  General  The- 
ories       105 

XXVII.  Faraday's  Theory  of  Electrical  Polarization    .        .        .110 

XXVIII.  Voltaic  Electricity 115 

XXIX. 'Effects  of  Voltaic  Electricity     .        .        .        ...        .120 

XXX.  The  Electro-chemical  Theory 125 

XXXI.  Ohm's  Theory  of  the  Voltaic  Pile— Magnetism       .        .  131 
XXXII.  Electro-dynamics— Thermo-electricity       .    .  Ji/ -"•  'C'      .  137 

XXXIII.  The  Chemical  Nomenclature     .        .        .   ••.'»".•        .144 

XXXIV.  The  Symbols       .        .       Y:  •  >       .        .        .  .147 
XXXV.  The  Laws  of  Combination         ....                .151 

XXXVI.  Constitution  of  Bodies— Crystallization    .  .155 

XXXVH.  Chemical  Affinity .164 


X  CONTENTS. 

Lecture  r*  -— •    "\  Page 

XXXVIII.  Pneumatic  Chemistry— Oxygen  Gas     .  .  169 

XXXIX.  Oxygen  (continued) 174 

XL.  Hydrogen        .        . 178 

XLI.  "Water 183 

XLII.  Nitrogen — Atmospheric  Air 188 

XL  III.  Atmospheric  Air  (continued)  .  .        .        .        .194 

XLIV.  Atmospheric  Air  (continued) 199 

XLV.  Compounds  of  Nitrogen  and  Oxygen    ....  205 
XL VI.  Compounds  of  Nitrogen  and  Oxygen     .        .  .  208 

XL VII.  Sulphur .  212 

XL VIII.  Compounds  of  Sulphur  and  Oxygen      .  .        .  217 

XL  IX.  Sulphur  and  Phosphorus          ...  .  220 

L.  Compounds  of  Phosphorus  and  Oxygen         .        .        .  224 

LI.  Chlorine  ...  228 

LII.  Chlorine  (continued) 232 

LIEI.  Bromine — Fluorine — Carhon 237 

LIV.  Carbonic  Acid 241 

LV.  Cyanogen — Boron — Silicon — Ammonium        .        .        .  245 

LVI.  General  Properties  of  the  Metals 252 

LVII.  Potassium 256 

LVIII.  Sodium — Lithium — Barium 260 

LIX.  Strontium — Calcium — Magnesium — Aluminum      .        .  266 

LX.  Manganese — Iron 274 

LXI.  Iron— Nickel— Cobalt— Zinc 278 

LXII.  Cadmium — Tin — Chromium — Titanium          .        .        .  283 

LXIII.  Arsenic 287 

LXIV.  Arsenic — Antimony — Tellurium — Uranium — Copper     .  291 

LXV.  Lead— Bismuth— Silver 297 

LXVI.  Mercury — Gold — Platinum,  &c 302 

LXVII.  General  Properties  of  Organic  Bodies   .        .        .        .307 

LXVni.  The  Non-nitrogenized  Bodies 311 

LXIX.  Action  of  Agents  on  the  Starch  Group  ....  315 
LXX.  The  Metamorphosis  of  the  Starch  Group  by  Nitrogen- 

ized  Fermenta 319 

LXXI.  The  Derivatives  of  Fermentative  Processes          .        .  323 
LXXIL  The  Derivative  Bodies  of  Alcohol  .        .        .327 

LXXIII.  Oxydation  of  Alcohol 330 

LXXIV.  Derivatives  of  Acetyle — the  Kakodyle  Group       .        .  334 

LXXV.  The  Wood  Spirit  Group 338 

LXXVI.  The  Potato  Oil  Group— the  Benzyls  Group  .  .  .342 
L  XXVII.  The  Salicyle  and  Cinnamyle  Groups  .  .  .  .345 
LXXVIII.  The  Nitrogenized  Principles — Ammonia — Cyanogen  .  349 

LXXIX.  Bodies  allied  to  Cyanogen 354 

LXXX.  Mellone— Urea 358 

LXXXI.  The  Vegetable  Acids 362 


CONTENTS.  XI 

Lecture  Pago 

LXXXII.  The  Vegetable  Alkalies 367 

LXXXni.  The  Coloring  Principles 371 

LXXXIV.  The  Patty  Bodies 375 

LXXXV.  The  Resins,  Balsams,  and  Bodies  arising  in  destructive 

Distillation 380 

L  XXXVI.  Animal  Chemistry — Digestion  and  Nutrition         .        .  384 
LXXXVII.  Origin  and  Deposit  of  the  Fats  and  Neutral  Nitrogen- 

ized  Bodies 387 

LXXXVIH.  The  Transmission  of  Food  through  the  System     .        .  392 
LXXXIX.  Nature  of  the  Processes  of  Secretion  . .       .       .       .395 


INTRODUCTION. 

CONSTITUTION  AND  GENERAL  PROPERTIES  OF  MATTER. 


LECTURE  >!'  ^  ;    n;vNa£  \\ 

CONSTITUTION  OP  MATTER. — Distinction  between  Chem- 
istry and  Natural  Philosophy. — General  Division  of 
Chemistry. — Active  Forces  and  Ponderable  Bodies. — 
Proof  of  the  Atomic  Constitution  of  Matter  in  the  Cases 
of  a  Solid  and  a  Gas. — Atoms  are  inconceivably  small. — 
They  are  not  in  contact. —  They  are  unchangeable  and 
indestructible. 

THE  physical  sciences  are  divided  into  two  classes,  com- 
prehended respectively  under  the  titles  of  NATURAL  PHI- 
LOSOPHY and  CHEMISTRY. 

Natural  Philosophy  investigates  the  relations  of  masses 
to  one  another.  The  movements  of  tides  in  the  sea  un- 
der the  conjoint  influence  of  the  sun  and  moon ;  the  de- 
scent of  falling  bodies-  to  the  earth ;  the  pressure  of  the 
atmosphere  ;  the  various  modes  of  rendering  mechanical 
forces  available,  by  the  action  of  levers,  pulleys,  wedges, 
screws;  the  phenomena  of  the  planetary  bodies,  which 
move  in  elliptic  orbits  around  a  central  mass :  these  are 
all  objects-  for  the  consideration  of  Natural  Philosophy. 

Chemistry  considers  the  relations  of  particles  to  each 
other  ;  it  investigates  the  properties  and  qualities  of  differ- 
ent kinds  of  matter,  their  mutual  influence,  and  the  ac- 
tion of  the  imponderable  principles  upon  them.  It  treats 
of  the  causes  of  those  invisible  movements  which  the 
molecules  of  bodies  around  us  unceasingly  undergo.  It 
also  includes  many  of  the  phenomena  of  living  beings, 
explains  the  objects  of  respiration,  digestion,  and  other 
such  animal  functions. 

Every  change  taking  place  in  bodies  is  due  to  the  op- 
eration of  some  active  force.  It  is  one  of  the  first  princi- 

Into  what  classes  are  the  physical  sciences  divided  ?  Of  what  phenom- 
ena tlons  natural  philosophy  treat?  What  are  the  objects  of  chemistry  ? 

A 


2 


CONSTITUTION    OF    MATTER. 


pies  in  philosophy,  that  no  movement  or  mutation  can  oc- 
cur in  any  thing  spontaneously ;  we  must  always  refer  it 
to  a  disturbing  cause.  Under  the  influence  of  heat,  bodies 
increase  in  size ;  under  that  of  electricity,  some  are  dis- 
severed into  their  component  elements ;  under  that  of 
light,  vegetables  form  from  inorganic  materials  their  or- 
ganized structures.  The  science  of  chemistry  resolves 
:  'Itself,  thereforf;,  into  two  divisions :  the  first,  embracing  the 
consideration  of  the  active  forces  of  chemistry ;  the  sec- 
'',  r£>Ecj;  fhe  objects  on  which  those  forces  operate. 

\These  active  forces  are  Heat,  Light,  and  Electricity. 
By  the  older  chemists,  they  are  designated  as  imponder- 
able substances,  from  the  circumstance  that  they  do  not 
affect  the  most  sensitive  balances. 

We  can  form  no  idea  of  the  properties  of  bodies  dis- 
engaged from  the  influence  of  these  principles.  Thus 
we  find  all  material  substances  existing  under  one  of 
three  conditions,  solid,  or  liquid,  or  gaseous;  and  the 
majority  can  assume  either  of  these  conditions  under  the 
influence  of  heat.  Water,  for  instance,  at  low  tempera- 
tures, exists  in  the  solid  state  as  ice ;  at  higher  tempera- 
tures, it  assumes  the  liquid  condition  ;  and,  at  still  higher, 
exhibits  the  gaseous  form.  We  see,  therefore,  that  it  is 
the  degree  of  heat  to  which  it  is  exposed  which  deter- 
mines its  physical  state. 

One  of  the  first  problems  which  the  chemist  has  to  solve, 
is  that  of  determining  the  true  constitution  of  matter ;  not 
of  matter  in  the  abstract,  but  as  placed  under  the  influence 
of  these  external  powers. 

All  the  phenomena  of  chemistry 
prove  that  material  substances  con- 
sist of  indivisible  and  exceedingly  mi- 
nute portions,  called  ATOMS,  which 
are  placed  at  certain  distances  from 
one  another,  those  distances  being 
variable  and  determined  by  the  agen- 
cy of  active  forces. 

Thus,  if  we  take  a  copper  ball,  a, 
Fig.  1,  an  inch  in  diameter,  and  provide  a  ring,  b,  of  such  a 

What  are  the  two  leading  divisions  of  chemistry  ?    What  are  the  act- 
ive forces  of  chemistry  ?     Why  are  these  called  imponderable  bodies  ? 
What  are  the  three  forms  of  substances  1     What  is  it  that  determines ' 
these  forms  ?    What  is  the  constitution  of  matter  ?     Describe  the  arrange- 
ment of  the  instrument  Fig.  I,  and  its  use. 


Fig.  1. 


CONSTITUTION  .OF    MATTER.  3 

size  that  the  ball  at  common  temperatures  can  readily  pass 
through  it,  and  having  suspended  the  ball  by  means  of  a 
chain  to  a  stand,  cl,  expose  it  to  the  flame  of  a  spirit  lamp, 
c,  as  it  becomes  warm  it  will  be  found  to  dilate,  so  that, 
in  -the  course  of  a  few  minutes,  it  can  no  longer  pass  read- 
ily through  the  ring,  but  if  placed  thereon,  remains  sup 
ported. 

While  under  these  circumstances  no  visible  change  has, 
taken  place  in  the  general  properties  of  the  ball ;  itt. 
weight  remains  the  same  as  before,  its  aspect  is  the  same. 
We  conclude,  therefore,  that  its  volume  has  increased  be- 
cause we  have  raised  its  temperature. 

But  now,  the  lamp  being  removed,  the  ball  still  resting 
on  its  ring,  begins  to  cool.  In  the  course  of  a  few  min 
utes  it  spontaneously  drops  through  the  ring.  It  has, 
therefore,  become  less  than  it  was  while  hot,  and,  in  poinl 
of  fact,  when  its  original  temperature  is  reached,  it  has  re- 
covered its  original  size. 

From  this  simple,  but  beautiful  experiment,  very  im 
portant  conclusions  may  be  drawn.  The  copper  ball,  in 
cooling,  becomes  less  :  a  fact  which  at  once  suggests  the 
idea  that  its  constituent  particles  have  approached  each 
other.  In  its  warm  and  dilated  state,  although  it  exhibit- 
ed no  appearance  of  transparency,  or  of  interstitial  spaces, 
or  pores  through  which  light  might  pass,  its  particles  were 
not  touching  one  another,  for  had  they  been  in  actual  con- 
tact they  could  not  have  more  closely  approached  one  an^ 
other,  and  contraction  could  not  have  taken  place. 

As  all  bodies  contract  during  the  act  of  cooling,  we  in- 
fer that  the  particles  of  which  they  are  composed  are 
separated  from  each  other  by  intervening 
spaces,  and  experiments  such  as  that  we 
have  been  considering  suggest  two  im- 
portant observations  :  1st.  That  all  mate- 
rial substances  are  made  up  of  small  par- 
ticles which  do  not  touch  each  other;  and, 
2d.  That  the  intervening  spaces  maybe  va- 
ried at  the  pleasure  of  the  experimenter. 
Let  us  consider  a  second  illustration 
which  will  lead  us  to  the  same  conclusion ;  selecting,.  as 

Why,  in  this  experiment,  does  the  ball  finally  drop  through  the  ring  ? 
Could  contraction  take  place  if  its  particles  wejre  already  in  contact  ? 
What  two  conclusions  do  these  facts  suggest  ? 


4  CONSTITUTION    OF    MATTER. 

the  object  of  our  experiment,  atmospheric  air,  a  substance 
differing  in  all  its  physical  and  chemical  relations  from 
the  copper  ball.  Let  us  take  a  tube  of  glass  half  an  inch 
in  diameter,  and  bent  in  the  form  exhibited  in  Fig.  2,  a, 
c,  d.  The  tube  is  closed  at  its  upper  end,  a  ;  it  is  bent 
at  c,  and  over  its  open  extremity,  at  d,  a  bag  of  India  rub- 
ber is  tied,  air  tight.  In  the  tube  there  has  been  previ- 
ously inclosed  a  sufficient  quantity  of  water  to  fill  all  the 
portion  b,  c,  d,  but  the  space  from  a  to  b  is  occupied  by 
atmospheric  air.  It  is  to  the  volume  of  this  atmospheric 
air  that  our  attention  is  directed. 

If  we  compress  the  India  rubber  bag  in  our  hand,  the 
Volume  of  the  air  instantly  becomes  less,  the  diminution 
being  greater  in  proportion  as  the  pressure  is  greater. 
Now,  it  is  inconceivable  that  this  phenomenon  should  en- 
sue, unless  the  aerial  particles  approached  each  other ; 
but  such  an  approach  would  be  impossible  if  they  were 
already  in  contact.  Two  particles  could  not  occupy  the 
same  space  at  the  same  time. 

We  conclude,  therefore,  that  for  atmospheric  air,  a 
gaseous  body,  as  well  as  for  copper,  a  solid,  the  same 
law  holds  good,  and  that  both  these  forms  of  matter  are 
constructed  upon  the  same  type ;  that  they  are  made  up 
of  particles  set  at  distances  from  one  another,  and  that  we 
can  change  those  distances  at  pleasure,  by  resorting  to 
changes  of  temperature,  or  to  mechanical  forces. 

Fig  3.  It  ls  worthy  of"  observation,  that  by  proper 

means  these  interstitial  spaces  may  be  greatly 
increased  or  diminished,  and  in  very  many  in- 
stances without  any  striking  apparent  change 
occurring  in  the  substance  under  experiment. 
Thus,  if  we  take  a  globe  of  glass  two  or  three 
inches  in  diameter,  a,  Fig.  3,  with  a  neck  or 
tube,  &,  proceeding  from  it,  and  fill  the  globe 
full  of  water,  with  the  exception  of  a  small  bubble  of  air 
which  occupies  its  upper  part,  while  the  open  extremity 
of  the  tube,  b,  dips  beneath  some  water  contained  in  a 
glass  jar,  c,  then,  covering  the  whole  with  an  air-pump 
receiver,  d,  proceed  to  exhaust,  we  shall  find  that  the  little 

Describe  the  instrument  represented  in  Fig:  2.  What  is  the  use  of 
this  instrument  ?  With  an  increase  of  pressure,  what  happens  to  the  in- 
cluded air?  Can  two  particles  occupy  the  same  space  at  the  same  time  ? 
What,  then,  is  the  deduction  from  this  experiment  ?  What  is  the  exper- 
iment given  in  Fig:  3  intended  to  illustrate  ? 


SIZE    OF    ATOMS.  5 

bubble,  a,  dilates  as  the  machine  is  worked,  and  may  be 
rendered  a  hundred-fold  greater  than  at  first.  In  this  ex- 
panded condition,  its  particles  must  have  greatly  reced- 
ed from  each  other,  and  yet  no  remarkable  physical  change 
is  to  be  observed.  There  are  no  dark  or  vacuous  spaces; 
but,  in  this  attenuated  condition,  it  possesses  the  aspect 
which  it  had  when  at  the  common  density. 

With  these  preliminary  facts,  we  may  now  direct  our 
attention,  1st,  to  the  properties  of  atoms ;  and,  2d,  to  the 
interstitial  spaces  which  part  them  from  each  other. 

That  the  atoms  of  which  bodies  are  composed  are  ex- 
ceedingly small,  we  possess  abundant  proof.  By  dissolv- 
ing substances  in  liquid  media,  and  then  greatly  diluting 
the  solution,  we  can  effect  a  subdivision  to  an  incredible 
extent.  A  single  drop  of  a  solution  of  sulphate  of  indigo 
will  communicate  a  blue  color  to  one  thousand  cubic  inch- 
es of  water,  so  that  every  drop  of  that  diluted  solution 
contains  a  portion  of  the  coloring  matter.  In  the  same 
manner,  by  resorting  to  proper  tests,  we  can  show  that  a 
grain  of  copper,  or  silver,  or  gold,  may  be  divided  into 
many  millions  of  smaller  parts,  each  of  which  may  be 
readily  recognized.  Nor  is  it  alone  by  these  chemical 
processes  that  such  a  minute  subdivision  may  be  effected  : 
by  th.e  mechanical  process  of  beating  with  a  hammer, 
gold  may  be  extended  into  leaves  which  are  less  than  the 
___i___  part  of  an  inch  thick,  a  dimension  far  less  than 
the  human  eye,  unassisted  by  microscopes,  can  discover, 
for  the  smallest  spherical  object  visible  to  it  is  about 
Y oVir  Part  °f  an  mcn  *n  diameter.  By  other  processes,  it 
has  been  estimated  that  this  metal  may  be  divided  to  such 
an  extent,  that  a  single  grain  will  yield  80  millions  of 
millions  of  visible  parts.  The  world  of  organization  fur- 
nishes us  with  still  more  striking  proofs.  There  exist 
animalcules  of  which  it  would  require  many  millions  to 
make  up  the  bulk  of  a  common  grain  of  sand,  yet  these 
are  furnished  with  digestive  and  respiratory  organs,  with 
circulating  juices,  and  with  contrivances  as  elaborate  as 
the  mechanism  of  the  highest  orders  of  life.  How  minute, 
then,  must  the  constituent  particles  be  ! 

To  what  extent  can  the  constituent  atoms  be  removed  ?  To  what  ex- 
tent can  sulphate  of  indigo  be  divided?  Can  similar  results  be  obtained 
from  metalline  bodies  ?  What  evidence  have  we  on  this  point  from  me- 
chanical processes?  What  argument  may  be  drawn  from  the  construe 
tion  of  animalcules  ? 

A  2 


4  CONSTITUTION    OF    MATTER. 

the  object  of  our  experiment,  atmospheric  air,  a  substance 
differing  in  all  its  physical  and  chemical  relations  from 
the  copper  ball.  Let  us  take  a  tube  of  glass  half  an  inch 
in  diameter,  and  bent  in  the  form  exhibited  in  Fig.  2,  #, 
c,  d.  The  tube  is  closed  at  its  upper  end,  a  ;  it  is  bent 
at  c,  and  over  its  open  extremity,  at  d,  a  bag  of  India  rub- 
ber is  tied,  air  tight.  In  the  tube  there  has  been  previ- 
ously inclosed  a  sufficient  quantity  of  water  to  fill  all  the 
portion  b,  c,  d,  but  the  space  from  a  to  b  is  occupied  by 
atmospheric  air.  It  is  to  the  volume  of  this  atmospheric 
air  that  our  attention  is  directed. 

If  we  compress  the  India  rubber  bag  in  our  hand,  the 
Volume  of  the  air  instantly  becomes  less,  the  diminution 
being  greater  in  proportion  as  the  pressure  is  greater. 
Now,  it  is  inconceivable  that  this  phenomenon  should  en- 
sue, unless  the  aerial  particles  approached  each  other ; 
but  such  an  approach  would  be  impossible  if  they  were 
already  in  contact.  Two  particles  could  not  occupy  the 
same  space  at  the  same  time. 

We  conclude,  therefore,  that  for  atmospheric  air,  a 
gaseous  body,  as  well  as  for  copper,  a  solid,  the  same 
law  holds  good,  and  that  both  these  forms  of  matter  are 
constructed  upon  the  same  type ;  that  they  are  made  up 
of  particles  set  at  distances  from  one  another,  and  that  we 
can  change  those  distances  at  pleasure,  by  resorting  to 
changes  of  temperature,  or  to  mechanical  forces. 

F(     3  It  is  worthy  of"  observation,  that  by  proper 

means  these  interstitial  spaces  may  be  greatly 
increased  or  diminished,  and  in  very  many  in- 
stances without  any  striking  apparent  change 
occurring  in  the  substance  under  experiment. 
Thus,  if  we  take  a  globe  of  glass  two  or  three 
inches  in  diameter,  a,  Fig.  3,  with  a  neck  or 
tube,  &,  proceeding  from  it,  and  fill  the  globe 
full  of  water,  with  the  exception  of  a  small  bubble  of  air 
which  occupies  its  upper  part,  while  the  open  extremity 
of  the  tube,  b,  dips  beneath  some  water  contained  in  a 
glass  jar,  c,  then,  covering  the  whole  with  an  air-pump 
receivjer,  d,  proceed  to  exhaust,  we  shall  find  that  the  little 

Describe  the  instrument  represented  in  Fig:  2.  What  is  the  use  of 
this  instrument  ?  With  an  increase  of  pressure,  what  happens  to  the  in- 
cluded air?  Can  two  particles  occupy  the  same  space  at  the  same  time  ? 
What,  then,  is  the  deduction  from  this  experiment  ?  What  is  the  exper- 
iment given  in  Fig.  3  intended  to  illustrate  ? 


SIZE    OF    ATOMS.  5 

bubble,  #,  dilates  as  the  machine  is  worked,  and  may  be 
rendered  a  hundred-fold  greater  than  at  first.  In  this  ex- 
panded condition,  its  particles  must  have  greatly  reced- 
ed from  each  other,  and  yet  no  remarkable  physical  change 
is  to  be  observed.  There  are  no  dark  or  vacuous  spaces; 
but,  in  this  attenuated  condition,  it  possesses  the  aspect 
which  it  had  when  at  the  common  density. 

With  these  preliminary  facts,  we  may  now  direct  our 
attention,  1st,  to  the  properties  of  atoms ;  and,  2d,  to  the 
interstitial  spaces  which  part  them  from  each  other. 

That  the  atoms  of  which  bodies  are  composed  are  ex- 
ceedingly small,  we  possess  abundant  proof.  By  dissolv- 
ing substances  in  liquid  media,  and  then  greatly  diluting 
the  solution,  we  can  effect  a  subdivision  to  an  incredible 
extent.  A  single  drop  of  a  solution  of  sulphate  of  indigo 
will  communicate  a  blue  color  to  one  thousand  cubic  inch- 
es of  water,  so  that  every  drop  of  that  diluted  solution 
contains  a  portion  of  the  coloring  matter.  In  the  same 
manner,  by  resorting  to  proper  tests,  we  can  show  that  a 
grain  of  copper,  or  silver,  or  gold,  may  be  divided  into 
many  millions  of  smaller  parts,  each  of  which  may  be 
readily  recognized.  Nor  is  it  alone  by  these  chemical 
processes  that  such  a  minute  subdivision  may  be  effected  : 
by  the  mechanical  process  of  beating  with  a.  hammer, 
gold  may  be  extended  into  leaves  which  are  less  than  the 
^o-oViTo-  -part  of  an  inch  thick,  a  dimension  far  less  than 
the  human  eye,  unassisted  by  microscopes,  can  discover, 
for  the  smallest  spherical  object  visible  to  it  is  about 
__L._  part  of  an  inch  in  diameter.  By  other  processes,  it 
has  been  estimated  that  this  metal  may  be  divided  to  such 
an  extent,  that  a  single  grain  will  yield  80  millions  of 
millions  of  visible  parts.  The  world  t)f  organization  fur- 
nishes us  with  still  more  striking  proofs.  There  exist 
animalcules  of  which  it  would  require  many  millions  to 
make  up  the  bulk  of  a  common  grain  of  sand,  yet  these 
are  furnished  with  digestive  and  respiratory  organs,  with 
circulating  juices,  and  with  contrivances  as  elaborate  as 
the  mechanism  of  the  highest  orders  of  life.  How  minute, 
then,  must  the  constituent  particles  be  ! 

To  what  extent  can  the  constituent  atoms  be  removed  ?  To  what  ex- 
tent can  sulphate  of  indigo  be  divided  1  Can  similar  results  be  obtained 
from  metalline  bodies  ?  What  evidence  have  we  on  this  point  from  me- 
chanical processes?  What  argument  may  be  drawn  from  the  construe 
tion  of  animalcules  ? 

A  2 


8  SIZE    OF    INTERSTITIAL    SPACES, 

force  of  the  earth,  the  force  of  gravitation,  is  of  a  certain 
intensity  on  the  surface  of  our  planet,  but  it  diminishes  as 
the  distances  become  greater.  The  forces  which  connect 
together  the  bodies  of  the  solar  system,  and,  indeed,  one 
planetary  system  with  another,  act  through  great  intervals 
of  space  ;  thus  the  attractive  force  of  the  sun,  operating 
through  many  millions  of  miles,  retains  the  earth  in  her 
orbit.  But  the  attractive  and  repulsive  forces  which  de- 
termine the  position  of  the  constituent  atoms  of  bodies  are 
limited  to  a  very  minute  space.  If  we  take  two  leaden 
bullets,'and  having  pared  a  small  portion  from  the  surface 
of  each,  so  as  to  expose  a  brilliant  metallic  spot,  bring 
them  within  an  inch  of  one  another,  they  exert  no  percep- 
tible attraction,  and  may  be  drawn  apart  with  the  utmost 
facility ;  we  may  diminish  the  distance  between  them  to 
the  tenth,  the  hundredth,  the  thousandth  part  of  an  inch, 
and  still  the  same  observation  may  be  made ;  we  may 
even  bring  them  in  apparent  contact,  and  the  attractive 
influence  of  the  particles  of '-the  one  upon  those  of  the  other 
is  still  undiscoverable ;  but,  on  pressing  them  together, 
we  can  finally  bring  them  within  the  range  of  each  other's 
influence,  and  then  they  cohere  together  as  though  they 
were  a  single  mass,  and  require  a  considerable  effort  to 
separate  them. 

The  apparatus  figured  in  the  margin  serves  to  illustrate 
F-    5  the  same  result.     Suspend  a  cir- 

cular piece  of  plate  glass,  a,  Fig. 
5,  an  inch  in  diameter,  to  one  of 
the  arms  of  a  balance,  Z>,  c,  counter- 
poising it  on  the  opposite  arm  by 
weights  placed  in  the  scale  pan,  d. 
Beneath  the  plate  of  glass  place  a 
cup,  e,  containing  some  quicksilver, 
and  it  can  be  proved  that  so  long  as  the  glass  is  at  a  sen- 
sible distance  from  the  surface  of  the  quicksilver,  no  at- 
traction between  them  is  exhibited,  for  were  such  the 
case,  the  arm  of  the  balance  should  incline,  and  the  glass 
descend.  As  long  as  the  smallest  perceptible  space  inter- 
venes, no  attractive  action  is  developed ;  but  on  bringing 
the  two  surfaces  in  contact,  they  cohere  ;  and  now  it  re- 
Through  what  spaces  can  these  forces  operate  ?  How  can  this  be  proved 
l>y  leaden  ballets  ?  Describe  the  apparatus,  Fig.  5.  What  is  its  use  ? 
What  the  fact  which  is  proved  by  it  ? 


CONSTITUTION    OF    MATTER.  9 

quires  the  addition  of  a  considerable  weight  in  the  scale 
pan  to  draw  them  asunder.  This  result  does  not  depend 
on  the  pressure  of  the  air,  for  it  equally  takes  place  in  a 
vacuum. 

From  experiments  of  this  kind,  therefore,  we  gather 
that  the  spaces  through  which  molecular  attractions  and 
repulsions  can  act  are  very  limited,  and  it  follows  of  ne- 
cessity that  the  interstices  which  separate  the  atoms  of 
bodies  are  exceedingly  minute,  for  through  those  spaces 
the  action  of  these  forces  extends.  If  the  limiting  distance 
through  which  molecular  attraction  and  repulsion  can 
reach  is* as  there  is  reason  to  believe,  from  some  of  the 
experiments  of  Newton,  less  than  the  millionth  of  an  inch, 
we  are  entitled  to  conclude  that  the  interstitial  spaces  are 
much  smaller. 

To  what,  then,  do  these  results  finally  point  in  regard 
to  the  constitution  of  matter,  if,  as  we  have  seen,  the  con- 
stituent atoms  themselves  are  inconceivably  minute,  and 
the  spaces  that  separate  them  as  small  as  we  have  reason  tc 
conclude  1  We  may  look  upon  the  universe  as  represent- 
ing on  a  grand  scale  the  constitution  of  matter  on  a  minute 
.one.  The  planetary  bodies  which  compose  the  solar  sys- 
tem, and  which  are  held  in  their  orbits  by  the  attraction 
of  a  central  mass,  are  separated  from  one  another  by  enor- 
mous spaces,  to  which  their  own  magnitudes  bear  but  an 
insignificant  proportion.  About  thirty  such  bodies,  great 
and  small,  compose  the  group  or  family  to  which  our 
earth  belongs.  But  as  there  are  systems  of  opaque  plan- 
etary bodies,  so  also  there  are  systems  of  self-luminous 
suns,  which  compose  together  colonies  of  stars.  In  the 
universe  myriads  of  such  systems  exist,  separated  from 
one  another  by  spaces  so  great  that  the  mind  can  form  no 
just  idea  of  them.  A  planet,  such  as  Jupiter  with  its  at- 
tendant satellites ;  a  self-luminous  star,  like  our  sun  with 
its  surrounding  bodies  ;  a  group  of  shining  stars,  such  as 
are  scattered  over  our  skies ;  a  collection  of  such  groups 
as  form  the  nebular  masses  ;  these,  in  succession,  furnish 
us  with  a  series  of  illustrations  on  a  scale  continually  in- 
creasing in  dimensions  of  the  constitution  of  matter,  which 
is  made  up  of  isolated  atoms  placed  at  variable  distances 

Does  the  experiment  depend  on  the  pressure  of  the  air  ?  What  are 
the  limiting  distances  through  which  molecular  forces  can  act  ?  State  the 
analogy  between  the  constitution  of  the  universe  and  the  constitution  of 
matter  ? 


10  CONSTITUTION    OF    MATTER. 

from  each  other,  the  size  of  these  atoms  bearing  an  insig- 
nificant proportion  to  the  spaces  intervening  between  them. 
The  human  mind  is  so  constituted  that  it  is  unable  to 
appreciate  whatever  is  exceedingly  great  or  exceedingly 
small.  We  can  neither  attach  a  precise  idea  to  the  mag- 
nitudes and  grander  relations  of  the  universe,  nor  to  the 
atomic  constitution  of  a  grain  of  dust.  Hereafter,  when 
we  come  to  speak  of  the  phenomena  of  light,  we  shall  see 
that  by  following  the  same  philosophical  methods  which 
have  been  cultivated  with  such  success  in  astronomy,  and 
which  have  furnished  us  with  a  general  view  of  the  con- 
stitution of  the  universe,  we  also  can  obtain  a  general  view 
of  the  scale  which  has  been  used  in  the  constitution  of 
material  bodies,  a  scale  which  brings'before  us  new  ideas 
of  time  and  space.  When  we  are  told  that  in  the  mill- 
ionth part  of  a  second  a  wave  of  violet  light  pulsates  or 
trembles  seven  hundred  and  twenty-seven  millions  of 
times,  and  that,  if  we  divide  a  single  inch  into  ten  millions 
of  equal  parts,  this  violet  wave  is  only  one  hundred  and 
sixty-seven  of  such  parts  in  length,  we  obtain  a  glimpse 
of  the  scale  on  which  material  bodies  are  composed,  and 
must  confess  the  inability  of  the  human  imagination  to 
form  a  proper  conception  of  such  results,  though  we  may 
feel  a  just  pride  in  the  intellectual  power  which  has  ascer- 
tained them. 


'•* 


PART  I. 

THE  FORCES  OF  CHEMISTRY. 

LECTURE  III. 

HEAT. — Preliminary  Ideas  of  the  Nature  of  Heat. — In- 
fluence of  Heat  in  the  inorganic  and  organic  Worlds, — 
Modes  of  Transference. — Illustrations  of  Expansion. — 
Heat  determines  the  Magnitude  and  Form  of  Bodies — 
Affects  our  Measures  of  Time  and  Space— Determines 
the  Distribution  of  Animals  and  Plants.  • 

WRITERS  on  chemistry  signify  by  the  term  Caloric,  the 
agent  which  excites  in  our  bodies  the  sensation  of  heat. 
By  some,  however,  heat  and  caloric  are  used  synonymous- 
ly. Those  who  look  upon  this  force  as  if  it  were  a  ma- 
terial and  imponderable  substance,  ascribe  to  the  particles 
of  caloric  a  self-repulsive  power,  and  an  attraction  for 
the  particles  of  ponderable  bodies. 

So  great  is  the  control  which  caloric  exercises  over  all 
kinds  of  chemical  changes,  that  few  experiments  can  be 
made  in  which  transformations  of  substances  take  place 
without  contemporaneous  disturbances  of  temperature. 
In  some,  heat  is  evolved  ;  in  others,  cold  is  produced.  To 
this  agent,  moreover,  we  so  constantly  resort  for  the  pro- 
motion of  molecular  changes,  that  the  chemist  has  been 
not  inaptly  designated  the  Philosopher  by  Fire. 

It  is  not  alone  in  the  inorganic  world  that  the  influences 
of  caloric  are  traced.  Life  can  not  take  place  except 
within  certain  limits  of  temperature ;  limits  which  are 
comprehended  between  the  freezing  and  the  boiling  points 
of  water,  that  is,  within  one  hundred  and  eighty  degrees 
of  our  thermometer ;  and,  in  point  of  fact,  within  a  nar- 
rower range  than  that.  It  is,  therefore,  not  alone  in 
chemistry,  but  also  in  physiology,  that  the  relations  of 
this  agent  are  of  interest. 

"What  is  caloric  ?  What  is  heat  ?  On  the  hypothesis  that  caloric  is 
an  imponderable  substance,  what  are  its  properties  ?  Why  is  it  that  the 
study  of  caloric  is  of  such  great  importance  in  chemistry  ?  Within  what 
limits  of  temperature  can  living  things  exist? 


12  HEAT    PRODUCES    EXPANSION. 

When  an  ignited  mass,  as  a  red-hot  ball,  is  placed  in 
the  middle  of  a  room,  common  observation  satisfies  us 
that  it  rapidly  loses  its  heat ;  its  temperature  descending 
until  it  becomes  the  same  as  that  of  surrounding  walls 
and  other  bodies.  This  loss  is  due  to  several  causes.  A 
part  of  the  heat  is  carried  away  by  contact  with  the  body 
which  supports  the  ball,  a  part  by  certain  motions  estab- 
lished in  the  surrounding  air,  and  a  part  by  radiation. 
This  removal  passes  under  the  name  of  transference,  and 
as  soon  as  the  temperature  has  declined  to  that  of  the  ad- 
jacent bodies,  an  equilibrium  is  said  to  have  been  attained. 
There  are  two  methods  by  which  caloric  can  be  trans- 
ferred :  1st.  By  radiation ;  2d.  By  convection.  Of  the 
former  we  have  two  varieties — general  radiation,  and  in- 
terstitial radiatyon. 

Fig.  6.  Under  the  influence  of  an  increasing  tempera- 
ture substances  expand.  This  takes  place,  what- 
ever their  form  may  be,  whether  solid,  liquid,  or 
gaseous.  The  experiment  which  is  illustrated  by 
Fig.  1,  establishes  this  fact  in  the  case  of  a  copper 
ball ;  and  that  the  same  law  holds  good  for  liquids, 
may  be  proved  by  taking  a  glass  tube,  a,  b,  Fig. 
6,  open  at  the  extremity,  <z,  but  having  a  bulb,  c, 
blown  upon  it  at  the  other  end.  The  bulb  and  a 
part  of  the  tube,  as  high  as  b,  is  to  be  filled  with 
any  liquid  substance,  such  as  water,  spirits  of  wine,  or 
Fig.  7.  °il  5  and  the  heat  of  a  lamp,  d,  applied.  As  the 
liquid  becomes  warm,  it  dilates,  as  is  shown  by  its 
rising  in  the  tube;  the  dilatation  increasing  with 
the  temperature. 

If  now  the  liquid  be  removed  from  the  bulb,  and 
the  tube  be  inverted,  as  shown  in  Fig.  7,  in  a  glass 
of  water,  we  can  prove  the  same  fact  for  gaseous 
substances,  taking,  as  the  type  or  representative  of 
them,  atmospheric  air;  for,  on  simply  grasping 
the  bulb,  c,  in  the  hand,  the  air  which  is  in  it  di- 
lates with  the  warmth,  and  bubbles  pass  in  succession 
from  the  open  end  of  the  tube,  through  the  water  in  the 
glass,  d. 

Through  what  causes  does  the  temperature  of  a  body  descend  ?  What 
is  meant  by  transference  and  by  equilibrium  ?  In  how  many  ways  can 
caloric  be  transferred?  How  many  varieties  of  radiation  are  there 1  By 
what  means  can  it  be  proved  that  solids,  liquids,  and  gases  expand  as 
their  temperature  rises,  and  contract  as  it  descends  ? 


EFFECTS    OP    HEAT.  13 

We  conclude,  therefore,  that  solids,  liquids,  and  gases 
expand  as  their  temperature  rises,  and  contract  as  their 
temperature  falls. 

The  magnitude  of  all  objects  around  us  is  determined 
by  their  temperatures.  A  measure  which  is  a  yard  long 
in  summer  is  less  than  a  yard  in  winter ;  a  vessel  which 
holds  a  gallon  in  winter  will  hold  more  than  a  gallon  in 
summer.  And  as  the  degrees  of  heat  vary  not  alone  at 
different  seasons  of  the  year,  but  also  during  every  hour 
of  the  day,  it  is  clear  that  the  dimensions  of  all  objects 
must  be  undergoing  continual  changes.  The  appearance 
of  stationary  magnitudes  which  such  objects  present  is 
therefore  altogether  a  deception. 

Heat  thus  determines  the  size  of  bodies ;  it  also  de- 
termines their  form.  As  we  have  said,  there  are  three 
forms  of  bodies,  solid,  liquid,  and  gaseous.  A  mass  of 
ice,  if  exposed  to  a  temperature  of  above  32°,  melts  into 
water;  and  if  that  water  be  raised  to  212°,  it  passes  into 
the  form  of  steam — a  gaseous  body.  The  assumption  of 
the  solid,  the  liquid,  or  the  gaseous  condition,  depends 
on  the  existing  temperature. 

In  the  same  manner  that  it  affects  our  measures  of 
space,  caloric  affects  our  measures  of  time.  Clocks  and 
watches  measure  time  by  the  vibrations  of  pendulums,  or 
the  oscillations  of  balance  wheels,  the  uniformity  of  the 
action  of  which  depends  on  the  uniformity  of  their  size. 
When  the  temperature  rises,  the  rod  of  a  pendulum 
lengthens,  and  its  vibrations  are  made  more  slowly;  the 
clock  to  which  it  is  attached  loses  time.  When  the 
temperature  declines,  the  pendulum  shortens;  it  beats  too 
quick,  and  the  clock  gains.  Similar  observations  may  be 
made  in  the  case  of  watches.  To  obviate  these  difficulties 
many  contrivances  have  been  invented,  such  as  the  grid- 
iron pendulum,  the  compensation  balance  wheel,  &c. 
Advantage  has  also  been  taken  of  such  substances  as  ex- 
pand but  little  for  a  given  elevation  of  temperature  ;  and 
thus  excellent  clocks  have  been  made,  the  pendulum  rods 
of  which  were  formed  of  a  slip  of  marble. 

The  natural,  as  well  as  the  artificial  measures  of  time, 
depend  on  the  influence  of  heat.  Our  unit  of  time — the 

Is  there  any  variation  at  different  seasons  in  the  length  of  measures  or 
the  capacity  of  vessels  ?  What  is  it  that  determines  me  form  of  bodies  ? 
How  can  caloric  affect  our  measures  of  time  ?  By  what  contrivances  haa 
this  difficulty  been  avoided  ? 

B 


14  CONNECTION    OF    TEMPERATURE    AND    TIME. 

day  —  is  the  period  which  elapses  during  one  complete 
rotation  of  the  earth  on  her  axis.  The  length  of  this  pe- 
riod is  determined  by  the  mean  temperature  of  her  mass. 
Should  the  mean  temperature  of  the  whole  earth  fall,  her 
magnitude  must  become  less,  or,  what  is  the  same  thing, 
her  diameter  must  shorten.  It  results  from  very  simple 
mechanical  principles,  that  a  given  mass,  the  dimensions 
of  which  are  variable,  rotating  on  its  axis,  will  complete 
each  rotation  in  a  shorter  space  of  time  as  its  diameter  be- 
comes smaller.  Thus,  when  we  tie  a  weight  to  the  end 
of  a  thread,  and,  swinging  it  round  in  the  air,  permit  the 
thread  to  wrap  round  one  of  the  fingers,  as  the  thread 
shortens  by  wrapping,  the  weight  accomplishes  its  revolu- 
tion in  a  less  period.  Now,  transferring  this  illustration 
to  the  case  before  us,  if  the  mean  temperature  of  the  earth 
had  ever  declined,  she  must  have  become  less  in  size,  and, 
therefore,  turned  round  quicker,  and  the  length  of  the  day 
must  have  necessarily  been  less.  But  astronomical  ob- 
servations, for  a  period  of  more  than  2000  years  back, 
prove  conclusively  that  the  length  of  the  day  has  not 
changed  by  so  small  a  quantity  as  the  -^  part  of  a  second, 
and  we  therefore  are  warranted  in  inferring  that  the  mean 
temperature  of  the  globe  has  not  perceptibly  fallen. 

The  distribution  of  heat  on  the  surface  of  the  earth  de- 
termines, for  the  most  part,  the  distribution  of  animals 
and  plants ;  to  each  climate  its  proper  denizens  are  as- 
signed. It  is  this  which  confines  the  lion  to  the  torrid  re- 
gions, and  the  white  bear  to  the  frigid  zone.  In  the  case 
of  man,  who  has  the  power  of  accommodating  his  diet  and 
his  dress  to  external  requirements,  almost  any  part  of  the 
earth  is  habitable.  Plants,  like  the  inferior  animals,  have 
their  localities  determined  chiefly  by  the  influence  of  heat. 
It  is  for  this  reason  that  even  in  tropical  climates,  if  we 
ascend  from  the  foot  to  the  top  of  a  very  high  mountain, 
we  successively  pass  through  zones  occupied  by  trees 
and  plants  which,  differing  strikingly  from  one  another, 
have  analogies  with  those  which  occupy  respectively  the 
torrid,  the  temperate,  -and  the  frigid  zones,  on  the  general 
surface  of  the  earth. 

:  Dolhese  disturbances  affect  the  natural  as  well  as  the  artificial  meas- 
ures of  time  ?  How  can  it  be  proved  that  the '-mean  temperature  of  the 
earth  has  not  for  many  centuries  changed  ?  What  is  it  that  chiefly  de- 
termines the  distribution  of  plants  and  animals  ? 


EXPANSION    OF    GASES.  15 


LECTURE  IV. 

EXPANSION  OF  GASES  AND  LIQUIDS. — Rudberg^s  Law. — 
Regularity  of  Gaseous  Expansion. — Ascentional  Power 
of  expanded  Gas. — Amount  of  Air  contained  in  the  same 
Volume  at  different  Temperatures. — Gas  Thermometers. 
— Expansion  of  Liquids. —  The  Mercury  Thermometer. 

IF  we  compare  together  the  three  forms  of  bodies,  as 
respects  their  changes  of  volume  under  the  influence  of 
heat,  we  shall  find  that  for  a  given  rise  of  temperature, 
gases  expand  the  most,  liquids  intermediately,  and  solids 
least  of  all.  To  this  rule  but  few  exceptions  are  known  ; 
liquid  carbonic  acid,  however,  expands  about  four  times 
as  much  as  any  gaseous  body. 

Recent  experiments  have  proved  that  gases  differ  among 
themselves  in  expansibility,  though  the  differences  are 
not  to  any  great  extent.  For  the  permanently  elastic 
gases,  atmospheric  air  may  be  taken  as  the  type ;  the  ex- 
periments of  Rudberg  show  that  it  expands  ^£3-  of  its 
volume  at  32°  for  every  degree  of  Fahrenheit's  ther- 
mometer. As  the  same  quantity  of  gas  occupies  very 
different  volumes  at  different  temperatures,  it  is  necessary, 
in  this  and  other  such  cases,  to  state  some  specific  tem- 
perature at  which  the  estimate  of  its  volume  is  made; 
the  same  gaseous  ma'ss  occupies  a  much  greater  space  at 
75°  than  it  does  at  32°.  In  the  instance  before  us,  we 
consider  the  original  volume  to  be  that  which  the  gas 
would  have  at  32°,  and  as  has  been  said,  every  degree 
above  that  point  will  increase  the  volume  by  Ti^  of  the 
bulk  it  then  possessed. 

Gases  expand  with  uniformity  as  their  temperature  in- 
creases. Ten  degrees  of  heat  produce  the  same  relative 
effect,  whether  applied  at  a  low  or  at  a  high  temperature ; 
this  regularity  probably  arises  from  the  want  of  cohesion 
which  the  gaseous  particles  exhibit ;  as  we  shall  presently 
see,  it  is  not  observed  in  the  case  of  liquids  and  solids. 

Of  solids,  liquids,  and  gases,  which  expand  most  by  heat?  In  what 
respect  is  liquid  carbonic  acid  peculiar  ?  Is  there  any  difference  among 
gases  in  their  rates  of  expansion  ?  What  is  Rudberg's  estimate  of  the 
amount  of  expansion  of  air?  "Why  are  we  required  in  these  cases  to 
adopt  a  specific  temperature  ?  Do  gases  expand  uniformly. 


16  EXPANSION    OF    GASES. 

The  change  in  specific  gravity  of  atmospheric  air,  when 
Fi    g  it  is  warmed,  is  the  cause  of  the  rise  of 

Montgolfier  balloons.  These,  which 
were  invented  in  France  in  the  year 
1782,  consist  of  a  bag,  or  globe,  of  light 
materials,  such  as  paper  or  silk,  with  an 
aperture  at  the  lower  part,  through 
which,  by  the  aid  of  combustible  ma- 
terial, as  straw  or  shavings,  the  air  in 
the  interior  may  be  rarefied.  On  a 
small  scale,  they  may  be  made  of  thin 
tissue  paper,  pasted  together  so  as  to 
form  a  sphere  of  two  or  three  feet  in  diameter,  an  aperture 
being  cut  in  the  lower  portion  six  inches  or  more  in  width, 
and  beneath  it  a  piece  of  sponge,  soaked  in  spirits  of  wine, 
suspended.  This  being  set  on  fire,  the  flame  rarefies  the 
air  in  the  interior  of  the  balloon,  which,  though  it  might 
be  at  first  flaccid,  soon  dilates,  and  the  whole  apparatus 
will  now  rise  in  the  air,  precisely  on  the  same  principle 
that  a  cork  rises  from  the  bottom  of  a  vessel  of  water. 

From  the  circumstance  that  the  volume  of  air  changes 
so  readily  with  changes  of  temperature,  contracting  under 
the  influence  of  cold,  and  dilating  under  that  of  heat,  it  is 
plain  that  in  different  climates,  on  the  earth's  surface  a 
very  different  amount  of  atmospheric  air  is  included  under 
the  same  measure.  A  vessel  which  will  hold  precisely 
one  ounce  weight  at  the  mean  temperature  of  New  York, 
will  hold  more  than  an  ounce  in  the  cold  polar  regions, 
and  less  than  an  ounce  in  the  tropics.  In  t'he  former  sit- 
uation the  air  is  more  dense,  because  it  is  in  a  contracted 
condition  by  reason  of  the  low  temperature,  and  therefore 
a  greater  weight  is  included  under  a  given  volume ;  in 
the  latter,  the  reverse  is  the  case.  These  facts  are  sup- 
posed to  be  connected  with  certain  physiological  results, 
as  we  shall  hereafter  see. 

The  expansions  of  atmospheric  air  taking  place  with 
regularity  as  the  temperature  rises,  that  substance  is  oc- 
casionally employed  as  a  means  of  thermometric  admeas- 
urement. The  air  thermometer,  called  also  Sanctorio's 
thermometer,  but  which  was  invented  by  Galileo  about 

What  are  Montgolfier  balloons,  and  why  do  they  rise  ?  Why  is  it  that 
the  weight  of  air  in  a  given  measure  is  different  at  different  places  ?  I)e« 
scribe  the  thermometer  of  Sanctorio.  By  whom  was  it  really  invented  ? 


GAS    THERMOMETERS. 


17 


Fig.  10. 


1603,  consists  of  a  tube  of  glass,  «,  Fig.  9,  ter- 
minated at  its  upper  extremity  by  a  bulb,  b  ;  the 
other  end  of  the  tube  being  open,  dips  beneath 
the  surface  of  some  colored  water  in  a  cup  or  res- 
ervoir, c,  which  serves  also  as  a  foot  or  support  to 
the  instrument.  The  bulb  and  part  of  the  tube 
are  full  of  air,  the  remainder  of  the  tube  is  occupi- 
ed by  the  colored  water,  which  by  its  movements 
up  and  down  serves  to  indicate  changes  in  the 
volume  of  the  included  air.  To  the  side  of  the 
tube  a  scale  of  divisions  is  affixed,  and  the  tube  is 
not  arranged  so  tightly  in  the  neck  of  the  reservoir  but 
that  there  is  a  free  passage  for  the  air  in  and  out  of  that 
part  of  the  instrument.  On  touching  the  ball  with  the 
fingers,  the  air  within  it  becomes  warm,  dilates,  and  de- 
presses the  liquid  in  the  tube,  or,  on  touching  it  with  any 
cold  body,  it  contracts,  and  the  liquid  rises. 

This  form  of  thermometer  is  liable  to  a  dif- 
ficulty which  renders  it  impossible  to  rely 
upon  its  indications,  except  under  particular 
circumstances.    It  is  affected  by  variations  of 
atmospheric  pressure,  as  well  as  by  changes 
of  heat.     To  prove  that  this  is  the  case,  place 
such  a  thermometer  under  the  receiver  of  an 
air  pump,  as  shown  in  Fig.  10  ;  on  producin 
the  slightest  degree  of  rarefaction,  the  liqui 
in  the  tube  is  instantly  depressed,  and  on  re- 
storing the  pressure  of  the  air,  it  returns  to  its  original 
position. 

The  differential  thermometer 
is  a  gas  thermometer,  so  arrang- 
ed as  to  be  free  from  the  .fore- 
going difficulty.  It  consists  of  a 
glass  tube,  a  b,  Fig.  11,  bent  into 
the  form  represented  in  the  fig- 
ure, with  a  bulb  blown  on  each 
extremity.  To  the  horizontal 
part  a  scale  of  divisions  is  affixed.  The  bulbs  are  full  of 
atmospheric  air,  and  in  the  tube  there  is  a  small  column 
of  colored  liquid,  which  serves  by  its  movements  as  an  in- 

How  can  the  use  of  this  instrument  be  illustrated  ?  By  what  disturb- 
ing cause  is  Sanctorio's  thermometer  affected  ?  How  may  that  be  proved  J 
Describe  the  differential  thermometer. 

B2 


Fig.  11. 


18 


EXPANSION    OF    LIQUIDS. 


Fig,  12. 


dex.  To  understand  the  action  of  this  instrument,  it  is 
only  necessary  to  consider  what  will  take  place  when  it  is 
carried  into  a  room  the  temperature  of  which  is  very  high 
or  very  low.  If  the  former,  the  air  in  both  bulbs,  becom- 
ing equally  warm,  will  expand  in  both  equally,  and  the 
column  of  fluid  which  acts  as  an  index  being  pressed 
equally  in  opposite  directions,  does  not  move  at  all.  If 
the  latter,  the  air  in  both  bulbs  cooling  equally,  contracts 
equally,  and  again  no  movement  ensues.  It  is  immateri- 
al, therefore,  whether  we  warm  or  cool  both  bulbs,  the 
instrument  is  motionless.  But  if  one  of  the  bulbs,  c,  is 
made  warmer  than  the  other,  d>  movement  at  once  ensues 
in  the  liquid  column  from  c  toward  d.  Movement  of  the 
index,  therefore,  takes  place  when  the  bulbs  are  at  differ- 
ent temperatures,  and  hence  the  instrument  is  called  a 
differential  thermometer.  It  was  formerly  of  considera- 
ble use  in  researches  connected  with  radiant  heat. 

Different  liquids  expand  different- 
ly for  the  same  thermometric  dis- 
turbance. This  is  easily  shown  by 
an  apparatus,  as  Fig.  12,  in  which 
we  have  three  tubes,  a,  b,  c,  with 
bulbs  on  their  ends,  dipping  into 
a  trough,  f,  of  tin  plate.  The  tubes 
and  bulbs  should  be  all  of  the  same 
size,  and  filled  with  the  liquids  to  be 
tried  to  the  "same  height.  To  each  a  scale  is  annexed. 
Let  a  be  filled  with  quicksilver,  b  with  water,  and  c  with 
alcohol ;  on  pouring  hot  water  into  the  trough,  two  phe- 
nomena are  witnessed:  1st.  All  the  liquids  expand;  2d. 
They  expand  unequally  when  compared  together,  the 
mercury  expanding  least,  the  .water  intermediately,  and 
the  alcohol  most. 

Unlike  gases,  all  liquids  expand  irregularly  as  their 
temperature  rises,  a  given  amount  of  heat  producing  a 
much  greater  effect  at  a  high  than  at  a  low  temperature. 
Ten  degrees  of  heat,  applied  to  a  given  liquid  at  200°, 
will  produce  a  greater  expansion  than  if  applied  at  100°. 
The  reason  appears  to  be,  that  as  a  liquid  dilates  its  co- 
if this  instrument  be  carried  into  a  warm  and  then  into  a  cold  room, 
does  its  index  move  ?  Why  is  it  called  differential  thermometer  ?  How 
can  it  be  shown  that  different  liquids  expand  differently  ?  Of  mercury, 
water,  and  alcohol,  what  is  the  order  of  expansion?  Do  liquids,  like  gas 
es,  expand  with  regularity  ?  What  is  the  cause  of  the  difference  ? 


6.  u 

, 


THE    MERCURIAL    THERMOMETER. 


19 


Fig.  13. 


hesive  force  becomes  less,  because  its  particles  are  being 
removed  farther  from  each  other ;  and,  as  the  cohesive 
force  weakens,  its  antagonistic  power,  the  heat,  produces 
a  greater  effect. 

Advantage  is  taken  of  the  properties  of  liquids 
in  the  making  of  thermometers.  For  these  pur- 
poses, alcohol  and  mercury  are  the  fluids  selected. 
The  mercurial  thermometer  consists  of  a  fine  cap- 
illary tube,  Fig.  13,  with  a  bulb  blown  on  one 
end  ;  the  bulb  and  part  of  the  tube  are  to  be  fill- 
ed with  quicksilver,  and  the  air  expelled  from  the 
rest  of  the  tube  by  warming  the  bulb  until  the 
metal  rises  by  expansion  to  the  top  of  the  tube, 
and  at  that  moment  hermetically  sealing  the  glass 
by  melting  the  end  of  it  with  a  blow-pipe.  As 
the  thermometer  cools,  the  quicksilver  retreats 
from  the  top  of  the  tube,  and  leaves  a  vacuum 
above  it. 

It  remains  now  to  annex  such  a  scale  to  the 
instrument  as  may  make  its  indications  compar- 
able with  other  instruments.  To  effect  this, 
the  thermometer  is  plunged  into  a  vessel  con- 
taining melting  ice  or  snow,  and  opposite  the 
point  at-  which  the  quicksilver  stands  is  marked 
32°.  It  is  then  transferred  to  another  vessel  in 
which  water  is  rapidly  boiling,  and  the  point  op- 
posite which  it  then  stands  is  marked  212°.  The  inter- 
vening space  is  divided  into  180  equal  parts;  these  are 
degrees,  and  similar  divisions  are  made  on  the  scale  for 
all  points  above  212°,  and  below  32°.  The  zero  point, 
or  cipher  of  the  scale,  is  therefore  32  degrees  below  the 
freezing  point  of  water. 

The  melting  of  ice  and  the  boiling  of  water  are  the  fix- 
ed thermometric  points.  They  have  been  selected  for  the 
purpose  of  rendering  thermometers  comparable  with  each 
other.  The  numbers  which  are  attached  to  these  points 
are  arbitrary,  and  accordingly  three  different  scales  have 
been  introduced  in  different  countries.  That  which  is 
commonly  used  in  America  and  England  is  the  Fahren- 

For  making  thermometers,  what  liquids  are  selected  ?  How  is  the  mer- 
curial thermometer  made  ?  Is  there  a  vacuum  above  the  mercury  in  the 
tube  ?  How  is  the  scale  adjusted  ?  "What  is  the  freezing  and  what  the 
boiling  point  ?  "What  is  meant  by  the  zero  ?  What  are  the  fixed  points  ? 
Why  are  these  fixed  points  employed  ?  What  three  scales  have  been 
introduced  ? 


20  THE    MERCURIAL    THERMOMETER. 

heit  scale,  which,  *as  we  have  just  seen,  makes  the  melting 
point  of  ice  32°,  and  the  boiling  of  water  212°.  In 
France,  the  Centigrade  scale  is  employed ;  this  has  for 
the  melting  of  ice  0°,  and  for  the  boiling  of  water  100°. 
In  some  parts  of  Europe,  Reaumur's  scale  is  used,  the 
points  of  which  are  respectively  0°  and  80°.  Chemical 
authors  always  specify  the  thermometer  they  use  by  a 
letter  attached  to  the  numbers  ;  thus,  212  F,  100  C,  80  R, 
refer  to  the  boiling  of  water  on  Fahrenheit's,  the  Centi- 
grade, and  Reaumur's  scales.  It  is  obvious  that  these  de- 
grees are  readily  convertible  into  each  other  by  a  simple 
arithmetical  process. 


LECTURE  V. 

EXPANSION  OP  LIQUIDS  AND  SOLIDS. — Importance  of  the 
Thermometer. — Alcohol  Thermometer. — Point  of  Max- 
imum Density  of  Liquids. — Maximum  Density  of  Wa- 
ter connected  with  Duration  of  the  Seasons. — Expansion 
of  Solids. 

FROM  the  considerations  advanced  in  Lecture  III.,  we 
can  perceive  the  importance  of  the  thermometer.  As  all 
our  measures  of  space  and  time  are  affected  by  variations 
of  temperature,  the  thermometer,  which  measures  those 
variations,  must  necessarily  be  one  of  the  fundamental 
instruments  of  physical  science.  If  we  state  that'  a  given 
object  is  a  foot  long,  we  must  specify  the  temperature  at 
which  the  measure  was  taken,  for  at  a  Tower  temperature 
it  will  be  less  than  a  foot,  and  at  a  higher  it  will  be  more. 

There  are  several  peculiarities  which  quicksilver  pos- 
sesses that  eminently  fit  it  to  be  a  thermometric  fluid. 
1st.  It  can  always  be  obtained  in  a  state  of  uniform  purity. 
2d.  It  expands  with  greater  regularity  than  most  liquids, 
as  its  temperature  rises,  and  when  included  in  a  bulb  of 
glass,  as  in  the  common  instrument,  the  irregularity  of 
expansion  of  the  glass  almost  exactly  compensates  the  ir- 
regular expansion  of  the  quicksilver,  and  hence  the  true 

What  is  the  Centigrade  scale  ?  What  is  Reaumur's  ?  Can  these  be 
converted  into  each  other  ?  Why  is  the  thermometer  such  an  important 
instrument  ?  What  are  the  qualities  which  quicksilver  possesses  which 
fit  it  for  these  uses  ? 


MAXIMUM    DENSITY    OP    WATER.  21 

temperature  is  very  accurately  marked.  3d.  The  range 
of  temperature  between  the  points  of  solidification  and 
boiling  is  great,  the  former  being  — 39°  Fahrenheit,  and 
the  latter  at  662°  Fahrenheit ;  that  is,  about  seven  hundred 
degrees.  4th.  It  does  not  soil  or  moisten  the  tube  in 
which  it  is  contained,  nor  does  it  adhere  thereto,  but 
moves  up  and  down  with  facility.  5th.  It  is  affected  much 
more  readily  than  water  or  spirits  of  wine  by  a  given 
amount  of  heat,  as  we  shall  see  when  we  come  to  speak 
of  the  capacity  of  bodies  for  caloric. 

When  very  low  temperatures  have  to  be  measured, 
such  as  approach  or  are  below  the  freezing  point  of  quick- 
silver, we  resort  to  thermometers  filled  with  alcohol,  tinged 
with  some  coloring  matter  to  make  its  movements  vis- 
ible. This  fluid  requires  a  diminution  of  temperature  of 
more  than  180°  below  the  zero  of  our  scale  before  it 
solidifies,  and  hence  is  adapted  to  the  measurement  of 
low  temperatures. 

If  we  take  some  water  at  100°  Fahrenheit,  and,  placing 
it  in  a  vessel  in  which  we  can  observe  its  volume,  reduce 
its  temperature,  we  shall  find,  agreeably  to  the  general 
law  heretofore  given,  that  as  it  cools  it  contracts.  As  it 
successively  passes  through  80,  60,  50  degrees,  it  exhibits 
a  continuous  diminution ;  but  as  soon  as  it  has  fallen  be- 
low 39°,  although  it  may  still  be  cooling,  it  begins  to  ex- 
pand, and  continues  to  do  so  until  it  reaches  32°,  when 
it  freezes.  If  we  take  some  water  at  32°  and  warm  it, 
instead  of  expanding,  it  contracts,  until  it  reaches  39° ; 
but  from  that  point,  any  farther  elevation  of  temperature 
causes  it  to  obey  the  general  law,  and  it  expands. 

It  is  obvious,  therefore,  that  if  we  take  water  at  39°, 
it  is  immaterial  whether  we  warm  it  or  cool  it,  it  will  ex- 
pand. At  that  temperature,  therefore,  this  liquid  occu- 
pies the  smallest  bulk,  and  is  at  its  greatest  density,  for 
neither  by  cooling  nor  warming  can  we  reduce  it  to  small- 
er dimensions.  The  particular  thermometric  point  at 
which  this  takes  place  is  designated  "  the  point  of  maxi- 
mum density  of  water"  and  very  exact  experiments  show 
that  it  is  about  39-^°  Fahrenheit. 

Under  what  circumstances  are  alcohol  thermometers  used  ?  Does  water 
contract  regularly  when  cooled  from  100°  to  32°  1  Does  it  regularly  ex- 
pand when  wanned  from  32°  ?  At  what  thermometric  point  does*  that 
change  take  place  ?  What  is  the  designation  given  to  that  point?  Why 
js  that  designation  appropriate  ? 


22  POINTS    OF    MAXIMUM    DENSITY. 

There  are  many  liquids  which  thus  have  points  of  max- 
imum density,  and  which  expand  previous  to  assuming 
the  solid  form.  In  the  act  of  solidifying,  water  undergoes 
a  very  great  dilatation,  amounting  to  about  £th  of  its  vol- 
ume ;  this  is  the  reason  that  ice  floats  upon  it.  Several 
melted  metals  exhibit  the  same  phenomenon,  and  advan- 
tage is  taken  of  the  fact  in  the  arts.  The  alloy  of  which 
printers'  types  are  formed,  or  stereotype  plates  cast,  in  the 
act  of  solidifying,  expands,  and  hence  forces  itself  into 
every  part  of  a  mould  in  which  it  may  be  poured,  and 
copies  it  perfectly  ;  the  same  is  the  case  with  melted  cast 
iron.  But  it  is  impossible  to  obtain  good  castings  with 
such  a  metal  as  lead,  which  contracts  as  it  cools,  and  there- 
fore tends  to  separate  from  the  surface  of  the  mould,  or 
to  leave  vacant  spaces  in  it. 

The  fact  that  water  possesses  a  point  of  maximum  den- 
sity is  connected,  to  a  great  extent,  with  several  remark- 
able natural  phenomena ;  the  freezing  of  water  on  its 
surface  is  one  of  these  results.  If  the  water  contracted 
as  it  cooled,  the  colder  portions  would  descend,  and  rivers 
or  ponds  would  commence  to  freeze  at  the  bottom  first, 
the  solidification  advancing  steadily  upward.  Such  col- 
lections of  this  liquid  would,  during  the  course  of  a  win- 
ter, become  solid  masses  of  ice,  and  they  would  greatly 
prolong  that  season  of  the  year,  from  the  length  of  time 
required  to  thaw  them.  But  with  things  as  they  at  pres- 
ent exist,  the  coldest  water  is  the  lightest ;  it  floats  on  the 
warm  water  below ;  solidification  takes  place  on  the  sur- 
face, and  a  veil  or  screen  is  soon  formed  which  protects  the 
liquid  beneath.  When  the  warm  weather  of  spring  comes 
on,  the  ice  on  the  surface  is  in  the  most  favorable  posi- 
tion for  melting,  and  thus  the  point  of  maximum  density 
of  water  comes  to  be  connected  with  the  duration  of  the 
seasons. 

Fig.  14.  We  have  already  proved  by  the 

i  p^_^^_^g  jffl  instrument  represented   in    Fig.   1, 

that  solid  substances  dilate  as  their 

*  b    temperature  rises.    The  same  results 

may  be  made  very  apparent  by  the  apparatus,  Fig.  14. 

Are  there  other  liquids  which  have  points  of  maximum  density  ?  What 
advantage  is  taken  of  this  fact  in  the  arts  ?  Why  does  water  freeze  first 
on  its  surface  ?  How  is  it  that  these  facts  are  connected  with  the  dura- 
tion of  the  seasons  ? 


EXPANSION    OF    SOLIDS.  23 

Upon  a  strong  basis  or  wooden  board,  a  b,  let  there  be 
fastened  two  brass  uprights,  c  d,  with  notches  cut  in  them, 
so  as  to  receive  the  ends  of  the  metallic  bar,  e.  This  bar 
should  be  very  slightly  shorter  than  the  distance  between 
the  two  uprights,  that  when  it  is  placed  resting  in  their 
grooves,  if  we  take  hold  of  it  and  move  it,  it  will  make  a 
rattling  sound  as  we  push  it  backward  and  forward.  If 
now  we  pour  hot  water  upon  the  bar,  it  dilates,  as  is 
proved  on  restoring  it  to  its  position  between  the  uprights  ; 
it  will  no  longer  rattle,  for  it  occupies  the  whole  distance 
between  them,  and  perhaps  there  may  even  be  a  difficulty 
in  forcing  it  into  the  grooves. 

For  the  determination  of  very  small  spaces,  the  sense 
of  hearing  may  often  be  far  more  effectually  employed 
than  the  sense  of  sight. 

The  pyrometer,  F^-  15- 

of  which  we  have 
several  varieties,  is 
represented  in  Fig. 
15.  It  may  serve  to 
illustrate  the  fact 
that  solid  substan- 
ces expand  by  heat. 
It  consists  essen- 
tially of  a  metallic 
bar,  a  a,  resting  at 
one  end  against  an 
immovable  prop,  e,  the  other  end  bearing  upon  a  lever,  b. 
The  extremity  of  this  lever  presses  upon  a  second  lever, 
c,  which  also  serves  as  an  index.  Upon  the  index-lever 
a  spring  acts  so  as  to  oppose  the  lever  b,  and  the  point  of 
the  index  ranges  over  a  graduated  scale. 

If  now  lamps  be  applied  to  the  bar,  it  expands,  and  the 
pressure  taking  effect  on  the  lever,  puts  it  in  motion,  the 
index  traversing  over  the  scale.  On  removing  the  lamp 
the  bar  contracts,  and  the  spring  pressing  the  lever  in  the 
opposite  direction  as  soon  as  the  bar  is  cold,  brings  the 
index  back  to  its  original  point. 

How  does  the  instrument,  Fig:  14,  prove  that  a  metallic  bar  expands 
when  heated  ?  Describe  the  pyrometer  and  the  mode  of  using  it. 


24          CONTRACTION    AND    DILATATION    OF    SOLIDS. 


LECTURE  VI. 

EXPANSION  OF  SOLIDS. — Contraction  of  Solids. —  They 
expand  irregularly. — Different  Solids  expand  different- 
ly.— Points  of  Maximum  Density. — Metallic  Thermom- 
eters.— Nature  of  Tliermometric  Indications. 

IT  is  a  popular  error,  that  when  solid  bodies  have  been 
heated,  they  do  not  return,  on  cooling,  to  their  original  size. 
Without  resorting  to  any  experimental  proof,  a  few  sim- 
ple considerations  will  satisfy  us  on  this  point.  If  a  bar 
of  metal  be  exposed  for  a  length  of  time  in  the  open  air, 
it  will  of  course  be  subjected  to  continual  changes  of  tem- 
perature ;  whenever  the  sun  shines  on  it  it  will  expand, 
and  during  the  cold  night  it  will  contract.  If  now,  on 
cooling,  it  did  not  rigorously  come  back  to  its  original 
size,  but  remained  a  little  elongated,  we  should  observe  it 
increasing  from  day  to  day,  and  no  matter  how  minute  the 
difference  might  be,  in  the  course  of  time  it  would  become 
perceptible.  Public  edifices  in  cities  are  often  surround- 
ed by  railings  of  cast  iron,  which  are  constantly  exposed 
for  years  to  variations  of  heat  and  cold,  but  did  any  person 
ever  observe  them  to  grow  or  increase  in  size?  We 
conclude,  therefore,  that  soHd  bodies,  on  cooling  to  their 
original  temperature,  regain  their  original  bulk. 

By  linear  dilatation  we  mean  increase  in  one  dimension, 
as  in  length;  by  cubic  dilatation,  increase  in  all  dimensions, 
length,  breadth,  and  thickness.  Knowing  the  amount  of 
linear  dilatation  of  a  given  solid,  we  can  easily  ascertain 
its  cubic  dilatation,  by  multiplying  the  former  by  3.  This 
result  is  near  enough  for  practical  purposes. 

Solids  expand  increasingly  as  their  temperature  rises, 
a  phenonemon  already  observed  in  the  case  of  liquids, 
and  due  to  the  same  cause — a  diminution  of  the  cohesive 
force  of  the  particles,  because  of  their  increased  distance. 

Compared  with  one  another,  different  solid  substances 

"What  decisive  proof  can  be  eiven  that  solids,  on  cooling1  to  their  ori<rinal 
temperature,  come  back  to  their  original  size  ?  What  is  linear  dilatation  ? 
"What  is  cubic  dilatation  ?  How  can  the  former  be  converted  into  the 
latter  ?  Does  the  same  solid  expand  uniformly  or  increasingly  as  its  tem- 
perature rises  ? 


COMPENSATION    BARS.  25 

expand  differently  for  the  same  disturbance  of  tempera- 
ture. This  may  be  shown  by  having  bars  of  different 
metals,  but  of  precisely  the  same  lengths,  adjusted  to  the 
grooves  of  the  instrument,  Fig.  14.  If  a  bar  of  brass  and 
one  of  iron  be  compared,  it  will  be  found  that  the  brass 
expands  more  than  the  iron,  for  it  will  entirely  fill  the  dis- 
tance between  the  uprights,  while  the. iron  rattles  between 
them. 

This  difference  of  expansion  is  also  shown  when  two 
long  slips  of  metal  are  soldered  together  face  to  face.  If 
we  fasten  in  this  manner  a  slip  of  brass  to 
a  similar  slip  of  iron,  as  in  Fig.  16,  in  ^ 
which  a  a  is  the  slip  of  iron  and  b  b  the  c 
slip  of  brass,  at  common  temperatures  the 
compound  bar  is  adjusted  so  as  to  be 
straight,  but  if  hot  water  be  poured  upon 
it,  it  immediately  curves,  as  represented 
at  a  c,  the  strip  of  brass  being  on  the  out- 
side of  the  curve  ;  if,  on  the  other  hand,  it 
be  artificially  cooled,  the  curvature  is  in 
the  other  direction,  as  at  b  d,  the  iron  being  on  the  out- 
side of  the  curve.  All  this  is  obviously  due  to  the  fact 
that,  for  the  same  disturbance  of  temperature,  the  brass 
contracts  and  dilates  much  more  than  the  iron.  When 
the  temperature  is  raised,  the  brass  becomes  the  longer, 
and  compels  the  compound  bar  to  curve,  it  occupying  the 
greater  length  of  the  curve.  When  the  temperature  falls, 
the  brass  becomes  the  shorter,  and  the  bar  curves  in  the 
opposite  direction. 

By  taking  advantage  of  these  metallic  combinations, 
pendulums  and  balance-wheels  for  the  accurate  measure- 
ment of  time  have  been  constructed.  The  gridiron  pen- 
dulum and  the  compensation  balance  are  examples. 
-  There  are  some  metallic  bodies  which  exhibit  points  of 
maximum  density  in  the  solid  state.  Rose's  fusible  metal 
is  an  example.  When  heated  from  32°  to  111°,  it  ex- 
pands, but  after  that  point  it  contracts,  and  continues  to  do 
so  until  it  reaches  156°,  at  which  temperature  it  is  actu- 
ally less  than  it  is  at  32°.  From  this  point  it  again  ex- 
Do  different  solids  expand  alike  ?  Of  brass  and  iron,  which  expands 
most  1  Describe  the  construction  of  a  compound  bar,  and  the  effect  of 
warming  and  cooling  it.  "What  instruments  are  constructed  on  this  prop- 
erty ?  What  are  the  properties  exhibited  by  Rose's  fusible  metal  ? 


26 


METALLIC    THERMOMETERS. 


pands,  and  continues  to  do  so  until  it  melts,  which  takes 
place  at  about  201°  Fahrenheit. 

Liquid  thermometers  have  a  limited  range  of  indica- 
tion. They  can  not  be  exposed  to  degrees  of  heat  ap- 
proaching the  point  of  solidification,  for  then  their  move- 
ments become  irregular ;  neither  can  they  be  used  for 
degrees  near  their  boiling  point,  for  if  vapor  should  form, 
the  instrument  would  be  destroyed.  But  as  there  are 
many  metals  which  require  a  very  great  degree  of  heat 
to  melt  them,  it  might  be  expected  that  we  should  find 
among  this  class  bodies  well  suited  for  thermometric  pur- 
poses. The  instrument  given  in  Fig.  15  serves  to  illus- 
trate such  an  apparatus,  and  also  the  difficulties  encoun- 
tered in  its  use.  From  the  small  extent  to  which  metals 
expand,  this  form  of  instrument  requires  levers,  or  wheels, 
or  some  multiplying  machinery  connected  with  it,  to  make 
the  changes  more  perceptible ;  but  such  mechanical  con- 
trivances can  not  be  employed  without  the  introduction 
of  certain  causes  of  disturbance.  Friction  occurs  on  the 
centers  of  motion,  the  teeth  of  the  wheels  play  on  each 
other,  and  therefore  the  index,  instead  of  moving  with 
regularity  and  precision  as  the  expanding  bar  presses, 
moves  by  starts  often  of  several  degrees  at  a  time,  then  it 
pauses,  and  once  more  starts  again,  the  whole  movement 
being  incompatible  with  exactness. 

A  compound  strip  of  metal,  as  represented  in  Fig.  16, 
is  free  from  many  of  these  difficulties,  and  if  of  sufficient 
length,  it  will  indicate  temperatures 
with  great  delicacy.  A  modifica- 
tion of  this  instrument  is  known  un- 
der the  name  of  Breguet's  ther- 
mometer. It  consists  of  a  very  slen- 
der strip  of  platinum,  soldered  to  a 
similar  piece  of  silver,  and  curved 
into  a  helix,  or  spiral,  a  b,  Fig.  17. 
It  is  fastened  at  its  upper  extremity 
to  a  metallic  support,  c  c,  and  from 
its  lower  portion  an  index  projects, 
which  plays  over  a  graduated  circle.  The  expansion  of 
silver  is  more  than  twice  as  great  as  that  of  platina ; 

Why  can  not  liquid  thermometers  be  used  for  very  low  and  very  high 
temperatures  ?  What  difficulties  occur  in  the  use  of  this  instrument  ? 
Describe  Breguet's  thermometer. 


Pig.  17. 


INDICATIONS    OF    THE    THERMOMETER.  27 

when,  therefore,  the  temperature  of  the  thin  spiral  rises, 
curvature,  with  a  corresponding  motion  of  the  index,  takes 
place ;  arid  if  the  temperature  falls,  there  is  a  movement 
in  the  opposite  direction,  as  has  been  already  explained. 
This  Breguet's  thermometer  is  one  of  the  most  delicate 
instruments  we  have,  for  the  mass  of  the  spiral  is  so  small 
compared  with  the  mass  of  mercury  in  an  ordinary  ther- 
mometer, that  every  change  in  the  surrounding  tempera- 
ture is  followed  with  rapidity  and  precision. 

For  many  purposes  in  science  and  the  arts,  it  is  necessa- 
ry to  determine  temperatures  above  a  red  heat.  Darnell's 
pyrometer  is  intended  to  meet  these  occasions.  It  con- 
sists of  an  arrangement  by  which  the  expansion  of  a  bar 
of  iron  or  platinum,  while  exposed  to  the  heat  to  be  meas- 
ured, is  registered.  The  amount  so  registered  is  subse- 
quently determined  upon  a  divided  scale,  and  the  tem- 
perature estimated  therefrom.  By  the  aid  of  such  an 
instrument  very  high  temperatures  may  be  determined, 
and  thus  it  has  been  shown  that  brass  melts  at  1869° 
Fahrenheit,  copper  at  1996°,  gold  at  2200°,  and  cast  iron 
at  2786°. 

The  thermometer  is  commonly  regarded  as  a  measurer 
of  heat.  A  little  consideration  will  satisfy  us  that  it  is 
only  so  in  a  limited  sense ;  it  does  not  indicate  the  quan- 
tity of  heat  present  in  the  bodies  to  which  it  is  exposed, 
for  if  immersed  in  a  glass  of  water  and  a  bucket  of  water 
drawn  from  the  same  well,  it  stands  at  the  same  point ; 
but  of  course  there  are  very  different  quantities  of  caloric 
in  the  two  cases.  It  is  not,  therefore,  the  quantity  of  heat, 
but  the  intensity,  which  it  measures ;  that  is  to  say,  not  the 
quantity  abstractly,  but  the  quantity  contained  in  a  given 
space ;  and  in  the  mercury  thermometer,  that  space  is 
measured  by  the  volume  of  the  mercury  in  the  instrument 
itself.  It  does  not  tell  how  much  heat  is  absolutely  present 
in  the  substances  to  which  it  is  exposed  ;  and  though  it 
may 'stand  at  the  same  height  in  the  same  quantity  of  two 
different  liquids,  it  does  not  follow  that  those  liquids  con- 
tain the  same  amount  of  caloric,  as  we  are  immediately 
to  see. 

Why  is  this  instrument  so  sensitive  ?  Describe  the  principle  of  Darnell's 
pyrometer  ?  Give  the  melting  points  of  some  of  the  most  important  met 
als.  Does  the  thermometer  measure  the  heat  to  which  it  is  exposed  ? 
What  is  it,  then,  that  it  does  actually  measure  ?  What  is  meant  by  the 
intensity  of  heat  ? 


28  CAPACITY    OF    BODIES    FOR    HEAT. 


LECTURE  VII. 

CAPACITY  OP  BODIES  FOR  HEAT. — Methods  of  determining 
Capacities.-^-  Warming.  —  Melting. —  Cooling. —  Mix- 
ture.-— Comparison  between  the  Thermometer  and  Cal- 
orimeter.— Definition  of  Specific  Heat. 

MANY  years  ago  it  was  discovered  by  Boyle,  that  if  two 
bottles  of  the  same  size  and  form  were  filled  with  differ- 
ent liquids,  and  placed  before  the  fire  so  as  to  receive  its 
heat  equally,  their  temperature  did  not  rise  similarly; 
thus,  if  one  bottle  was  filled  with  water  and  the  other  with 
quicksilver,  the  temperature  of  the  latter  would  rise  much 
more  rapidly  than  that  of  the  former ;  and,  on  making 
the  experiment  with  a  little  care,  it  will  be  found  that  the 
same  quantity  of  heat  will  raise  the  temperature  of  mer- 
cury twice  as  high  as  that  of  an  equal  volume  of  water. 

By  extending  these  experiments  to  other  substances,  it 
has  been  fully  proved  that  different  bodies  require  different 
amounts  of  heat  to  warm  them  equally. 

There  are  several  different  methods  by  which  the  ca- 
pacity of  bodies  for  heat  may  be  determined,  such  as,  1st, 
by  warming;  2d,  by  melting;  3d,  by  cooling;  4th,  by 
mixture.  - 

The  first  of  these  ^methods  has  already  been  illustrated 
by  the  experiment  of  Boyle,  It  consists  essentially  in  ex- 
posing the  same  weight  of  the  substances  to  be  tried  to  a 
uniform  source  of  heat,  as,  for  example,  a  bath  of  hot  water, 
and  examining  how  high  their  temperature  has  risen  in  a 
given  space  of  time.  Thus  it  will  be  found  that  it  takes 
twenty-three  times  as  long  to  warm  water  as  to  warm 
mercury,  when  equal  weights  are  used,  and  hence  we 
infer  that  the  capacity  of  water  for  heat  is  twenty-three 
times  that  of  quicksilver. 

The  second  process  is  involved  in  the  action  of  the  cal 
orimeter,  the  operation  of  which  may  be  easily  under 
stood  from  Fig.  18.  Take  a  solid  block  of  ice,  a  a,  in 
which  a  cavity  of  the  form  represented  at  b  has  been 

Describe  Boyle's  experiment  with  water  and  quicksilver.  To  what 
general  result  do  such  experiments  lead  ?  State  the  different  methods  by 
which  capacities  for  heat  may  be  determined.  Give  an  illustration  of  the 
first  process. 


THE    CALORIiMETER. 


29 


made,  and  provide  a  slab  of  ice,  c  c,  Fis- 18- 

which  may  close  completely  the  mouth  c 
of  the  cavity.  Suppose  it  were  re- 
quired to  determine  the  relative  ca- 
pacities of  water  and  quicksilver  for 
heat.  In  a  glass  flask,  d,  place  one 
ounce  of  water,  •  and  by  immersing 
the  flask  in  a  bath  of  hot  water,  raise 
its  temperature  up  to  a  given  point, 
as,  for  example,  200° ;  then  place  the  flask  at  this  tem- 
perature in  the  cavity  &,  and  put  on  the  cover,  c  c.  The 
hot  water  in  the  flask  begins  to  cool,  and  in  descending  to 
32°,  the  point  to  which  it  will  eventually  come,  a  certain 
portion  of  the  surrounding  ice  is  melted,  the  water  re- 
sulting therefrom  collects  in  the  bottom  of  the  cavity,  and 
when  the  cooling  is  complete,  it  may  be  poured  out  and 
measured. 

In  the  next  place,  put  in  the  flask  one  ounce  of  quick- 
silver, the  temperature  of  which  is  raised  as  before  to 
200°  by  immersion  in  the  hot- water  bath ;  deposit  the 
flask  in  the  ice  cavity,  and  put  on  the  cover.  As  the  quick- 
silver cools,  the  ice  melts,  and  when  the  collected  water 
is  measured,  it  is  found  to  be  less  than  in  the  other  case, 
in  the  proportion  of  1  to  23.  A  given  weight  of  water 
will  therefore  melt  23  times  as  much  ice  as  an  equal 
weight  of  quicksilver,  in  cooling  through  the  same  number 
of  degrees. 

The  calorimeter  of  Lavoisier,  which  is  represented  in 
Fig.  19,  acts  on  the  same  prin- 
ciple as  the  block  of  ice.  It 
consists  of  a  set  of  tin  vessels 
within  each  other ;  in  the  cen- 
tral one,  a,  the  substance  to  be 
examined  is  placed,  and  be- 
tween this  and  the  next  vessel, 
at  5,  the  ice  to  be  melted  is 
introduced,  broken  into  small 
fragments;  the  water  arising 
from  the  melting  flowing  off 
through  a  stopcock,  c,  at  the 

Show  how  the  capacities  of  water  and  mercury  may  be  ascertained  by 
the  second.     What  are  the  relative  capacities  of  equal  weights  of  these 
bodies  ?    Describe  the  calorimeter  of  Lavoisier. 
C  2 


Fig.  19. 


30  METHODS    OF    DETERMINING    CAPACITIES. 

bottom  into  a  measuring  glass ;  and  in  order  to  avoid  any 
portion  of  the  ice  being  melted  by  the  warm  external  air, 
another  layer  of  fragments  of  ice  is  placed  on  the  outside 
at  d,  and  the  water  arising  from  it  is  carried  off  by  a  lat- 
eral stopcock,  e. 

The  third  process,  the  method  by  cooling,  known  also 
as  the  method  of  Dulong  and  Petit,  consists  essentially  in 
ascertaining  the  length  of  time  required  to  cool  through  a 
given  number  of  degrees.  A  substance  which,  like  water, 
has  a  great  capacity  for  caloric,  and  therefore  contains  a 
large  amount  of  it,  requires  a  greater  length  of  time  to 
cool ;  but  one  like  quicksilver,  the  capacity  of  which  is 
small,  having  less  heat  to  give  forth,  requires  a  corre- 
sponding short  space  of  time.  The  method  by  cooling  re- 
quires several  precautions;  among  others,  the  bodies  un- 
der investigation  should  be  placed  in  vacuo.  It  gives  very 
exact  results. 

The  method  by  mixture  may  be  readily  understood. 
If  a  pint  of  wrater  at  50°  be  mixed  with  a  pint  of  water  at 
100°,  the  temperature  will  be  75°,  that  is  the  mean.  But 
if  a  pint  of  mercury  at  100°  be  mixed  with  a  pint  of  wa- 
ter at  40°,  the  temperature  of  the  mixture  will  be  60°  : 
so  that  the  forty  degrees  lost  by  the  mercury  can  only 
raise  the  temperature  of  the  water  twenty  degrees.  It 
appears,  therefore,  that  when  equal  volumes  of  these  flu- 
ids are  examined,  the  capacity  of  the  water  for  heat  is 
about  twice  as  great  as  that  "of  mercury,  and  of  course  the 
result  becomes  still  more  striking  when  equal  weights  are 
used,  being  then,  as  we  have  seen,  in  the  proportion  of  1 
to  23. 

The  method  of  mixtures  is  not  limited  to  the  investiga- 
tion of  liquid  substances,  but  it  may  also  be  extended  to 
solids.  Thus,  if  a  pound  of  copper,  heated  to  300°,  be 
plunged  into  a  pound  of  water  at  50°,  the  resulting  tem- 
perature is  72°  ;  from  which  it  appears  that  the  capacity 
of  water  for  heat  is  about  ten  times  as  great  as  that  of 
copper. 

By  resorting  to  these  various  methods,  the  capacities 
of  a  great  number  of  substances  have  been  determined, 
and  in  the  treatises  on  chemistry,  tables  exhibiting  such 
results  are  given.  But  it  will  have  been  noticed,  from  the 

Describe  the  method  of  Dulong  aud  Petit.  Describe  the  method  by 
tiixture-  Is  this  limited  to  liquid  substances  ? 


BLACK'S  DOCTRINE  OF  CAPACITIES.  31 

foregoing  instances,  that  it  is  not  the  absolute  quantities  of 
heat  in  bodies  that  we  thus  determine,  but  only  relative 
quantities  in  substances  compared  together.  Such  ta- 
bles require,  therefore,  one  substance  to  be  selected  with 
which  all  the  others  may  be  compared,  and  for  solids  and 
liquids  water  has  been  chosen.  Its  capacity  for  heat  is 
represented  by  I'OOO,  and  with  it  they  are  compared.  For 
gaseous  bodies  atmospheric  air  is  chosen. 

By  contrasting  the  nature  of  the  results  given  by  the 
calorimeter,  Fig.  19,  with  the  indications  of  a  thermom- 
eter, we  shall  see  more  clearly  what  it  is  that  the  latter 
instrument  in  reality  points  out.  The  calorimeter  meas- 
ures quantities  of  heat,  the  thermometer  intensities.  As 
has  been  said,  a  thermometer  placed  in  two  vessels  of 
different  capacities,  filled  with  water  from  the  same  source, 
will  stand  at  the  same  height  in  both,  and  indicate  the 
same  temperature.  But  it  needs  no  experiment  to  assure 
us  that,  if  these  different  quantities  of  water  were  placed 
successively  in  the  interior  of  the  calorimeter,  they  would 
melt  different  quantities  of  ice,  the  one  melting  more  of 
the  ice  in  proportion  to  its  greater  weight  compared  with 
the  other. 

Dr.  Black,  who  was  one  of  the  early  investigators  of 
these  phenomena,  introduced  the  term  "Capacity  of  Bod- 
ies for  Heat,"  implying  the  idea  that  this  principle,  enter- 
ing their  pores,  could  be  taken  up  by  different  bodies  in  dif- 
ferent amounts.  Thus,  if  we  have  two  pieces  of  sponge 
of  the  same  size,  one  of  which  is  of  a  very  dense,  and  the 
other  of  a  porous  texture,  and  cause  them  to  imbibe  as 
much  \vater  as  they  can  hold,  the  porous  sponge  will  of 
course  contain  the  greater  quantity.  These  sponges  may 
therefore  be  said  to  have  different  "  capacities  for  water ;" 
and  this  is  precisely  the  idea  which  is  conveyed  in  Black's 
doctrine  of  capacity. 

But,  upon  these  principles,  it  would  follow  that  the 
lighter  a  body  is,  that  is,  the  greater  the  interstices  between 
its  atoms,  the  more  caloric  it  should  be  able  to  contain. 
Oil,  therefore,  which  will  float  upon  water,  ought  to  have 
a  greater  capacity  for  heat  than  water ;  but,  in  fact,  it  is 

Do  we  thus  determine  the  absolute  quantities  of  heat  in  bodies  ?  What 
substance  is  used  to  compare  solids  and  liquids?  "What  is  the  substance 
for  gases  ?  How  do  the  indications  of  the  calorimeter  compare  with  those 
of  the  thermometer  ?  On  what  analogy  is  Black's  doctrine  of  "  capacity" 
fouuded  ?  What  is  the  objection  to  this  doctrine  ? 


32  VARIATIONS    OF    SPECIFIC    HEAT. 


the  reverse,  for  its  capacity,  instead  of  being  greater,  isr 
not  one  half.  To  avoid  these  difficulties,  the  term  spe- 
cific heat  has  been  introduced  by  most  writers,  and  the 
term  capacity  abandoned,  a  change  which  I  think  is  to 
be  regretted. 

The  specific  heat  of  bodies,  or  their  capacity  for  calor- 
ic, increases  with  their  temperature.  Upon  Black's  doc- 
trine, the  cause  of  this  is  readily  understood,  for,  in  sim- 
ple language,  the  pores  become  larger,  and  there  is  there- 
fore room  for  more  heat.  Solid  substances,  when  violent- 
ly compressed,  evolve  a  portion  of  their  caloric  :  thus,  &• 
piece  of  soft  iron,  when  hammered,  becomes  red  hot, 
The  doctrine  of  Black  here  again  offers  a  ready  expla* 
nation,  for  on  the  same  principle  that  a  sponge,  when  com 
pressed,  allows  a  certain  portion  of  its  water  to  exude,  s* 
the  metalline  mass,  when  its  particles  are  forced  togethei  % 
allows  some  of  its  caloric  to  escape. 
<*? 

- 

LECTURE  VIII. 

CAPACITY  FOR  HEAT  AND  LATENT  HEAT.  —  Variability  of 
Capacity  under  Compression  and  Dilatation.  —  Theory  of 
the  Formation  of  Clouds.  —  The  Fire  Syringe.  —  Cold  in 
the  upper  Regions  of  the  Air.  —  Connection  between  Spe- 
cific Heats  and  Atomic  Weights*  —  Latent  Heat.  —  Ca- 
loric of  Fluidity. 

WHEN  the  volume  of  a  gas  increases,  its  capacity  for 
heat  increases,  and  a  diminution  of  volume  is  attended 
Fig.  20.      with  a  diminution  of  capacity.     Thus,  if  we 
CY       place  a  Breguet's  thermometer  under  the  re- 
ceiver of  an  air  pump,  and  exhaust  rapidly,  a 
sudden  reduction  of  temperature  is  indicated, 
arising  from  the  fact  that,  as  the  rarefaction  is 
effected,  the  capacity  increases,   an   increase 
which  is  satisfied  at  the  expense  of  a  portion  of 
the  sensible  heat. 

Upon  the  same  principle  we  can  explain  the  sudden 

"What  is  meant  by  specific  heat?  Does  the  capacity  of  bodies  change 
with  their  temperature  1  Does  it  change  tinder  compression  ?  How  is 
this  explained  agreeably  to  Black's  doctrine  1  When  the  volume  of  a 
gas  changes,  what  are  the  changes  in  its  specific  heat  ?  What  is  the 
fact  which  the  experiment  of  Fig-  20  proves  1 


FORMATION    OF    A    CLOUD. 


33 


appearance  of  a  fog  or  cloud,  when  moist  air  is  quickly 
rarefied.  It  will  be  seen,  when  I  come  to  speak  of  the 
nature  of  vapors,  that  the  quantity  of  vapor  which  can 
exist  in  a  given  space  depends  on  the  temperature ;  thus 
if  a  space  saturated  with  vapor  is  cooled,  a  portion  of  the 
vapor  assumes  the  liquid  form.  When,  therefore,  by 
the  aid  of  an  air  pump,  we  suddenly  rarefy  air  saturated 
with  moisture  under  a  receiver,  the  capacity  increases, 
cold  is  produced,  and  a  part  of  the  water  takes  on  the 
form  of  drops.  It  is  on  this  principle  that  the  Fig.  si. 
nephelescope  acts :  it  consists  of  a  receiver,  a, 
Fig.  21,  connected  with  a  flask,  c,  by  an  inter- 
vening stop-cock,  b  ;  the  stop-cock  being  closed, 
the  receiver  is  exhausted  by  the  pump,  and 
now,  on  suddenly  opening  the  stop-cock,  so  that 
the  air  contained  in  the  flask  may  rapidly  ex- 
pand into  the  receiver,  a  mist  or  cloud  makes 
its  appearance,  due  to  the  deposit  of  water  in 
the  form  of  minute  drops.  If  the  air  at  the  time 
be  very  dry,  it  may  be  purposely  rendered 
moist  by  being  exposed  to  water. 

When  atmospheric  air  is  suddenly  compressed,  its  ca- 
pacity for  heat  diminishes;  this  is  well  shown  by 
an  instrument  such  as  is  represented  in  Fig.  22, 
consisting  of  a  syringe,  with  a  piston  moving  per- 
fectly air  tight  in  it.  On  the  end  of  the  piston 
there  is  an  excavation,  in  which  a  piece  of  tinder 
may  be  fastened ;  the  piston  being  rapidly  forced 
into  the  syringe,  the  air  is  compressed,  the  capacity 
for  heat  becomes  less,  caloric  is  evolved,  and  the 
tinder  set  on  fire.  At  one  time  these  syringes  were 
used  as  a  means  of  obtaining  fire. 

The  variation  in  capacity  of  substances  under  variation 
of  volume  may  be  clearly  understood  and  readily  borne 
in  mind  by  Black's  doctrine,  as  illustrated  in  the  case  of 
a  moistened  sponge.  If  a  sponge  which  has  imbibed  as 
much  water  as  it  can  hold  be  compressed,  a  portion  of 
the  water  exudes,  just  as  the  air  in  the  syringe  allows  a 
portion  of  its  heat  to  escape  when  pressure  is  made.  On 

What  is  the  theory  of  the  production  of  clouds  ?  Describe  the  nephel- 
escope. What  is  the  result  of  the  action  of  this  instrument  ?  When  air 
is  compressed,  why  does  it  emit  heat  ?  How  can  these  changes  be  ac- 
counted for  by  Black's  doctrine  1 


34  SENSIBLE    AND    INSENSIBLE    HEAT. 

relaxing  the  force  on  the  sponge,  and  allowing  it  to  dilate, 
it  will  take  up  an  increased  quantity  of  water ;  and  air, 
when  suddenly  dilated,  as  we  have  seen,  has  its  capacity 
for  heat  increased. 

From  these  facts,  it  appears  that  the  heat  of  bodies 
exists  under  two  different  forms,  as  sensible  and  insensible 
heat.  In  the  experiment  with  the  syringe,  just  related, 
the  heat  that  sets  fire  to  the  tinder  existed  previously  to 
compression  in  the  air ;  it  existed  as  insensible  heat,  but 
during  the  compression  it  put  on  the  form  of  sensible  heat. 
The  same  transition  is  also  recognized  in  the  action  of  the 
nephelescope ;  the  heat,  which  was  sensible  before  rare- 
faction, becomes  insensible,  and  cold,  or  a  depression  of 
temperature,  is  the  result. 

The  great  degree  of  cold  which  reigns  in  the  upper 
regions  of  the  atmosphere  is  due,  to  a  considerable  extent, 
to  the  capacity  of  that  dilated  air  for  heat.  On  the  same 
principle  we  can  explain  the  formation  of  clouds  from 
transparent  atmospheric  air :  a  stratum  of  air,  reposing  on 
the  surface  of  the  sea,  or  the  moist  earth,  becomes  satu- 
rated with  vapor;  by  the  warmth  of  the  sun  or  other 
causes,  it  begins  to  rise  in  the  atmosphere,  and  as  it  rises 
it  expands,  because  the  pressure  upon  it  is  continually 
becoming  less.  An  increased  capacity  is  the  result  of  its 
dilatation,  and,  as  is  the  case  in  the  nephelescope,  cold  is 
produced,  and  a  deposit  of  a  part  of  the  moisture  takes 
place  ;  this  moisture,  appearing  under  the  form  of  minute 
drops,  is  what  we  call  a  cloud. 

From  the  small  capacity  of  quicksilver  for  heat,  we  see 
one  of  the  reasons  that  it  is  a  suitable  substance  for  form- 
ing thermometers;  it  warms  rapidly  and  cools  rapidly, 
and  therefore  follows  variations  of  temperature  much  more 
promptly  than  water  and  most  other  liquids. 

There  is  a  connection  between  the  specific  heat  of  sev- 
eral simple  bodies  and  their  atomic  weights,  pointing  out 
the  fact  that  elementary  atoms  ha,ve  in  many  instances 
the  same  specific  heat ;  recently  the  same  conclusion  has 
been  established  in  the  case  of  certain  oxides,  carbonates, 
and  sulphates. 

What  are  the  relations  between  sensible  and  insensible  heat  ?  De- 
scribe the  mode  in  which  clouds  form.  Why  does  the  capacity  of  quick- 
silver  fit  it  for  a  thermometric  liquid  ?  What  is  the  relation  of  the  specific 
beat  of  many  elementary  bodies  ? 


LATENT    HEAT.  35 

If  we  take  a  mass  of  ice,  the  temperature  of  which  is  at 
the  zero  p«int,  and  bring  it  into  a  warm  room,  examining 
the  circumstances  under  which  its  temperature  rises,  they 
will  be  found  as  follows :  the  mass  of  ice,  like  any  other 
solid  body,  warms  with  regularity  until  it  reaches  32° ; 
then,  for  a  considerable  period  of  time,  no  farther  eleva- 
tion is  perceptible,  but  it  undergoes  a  molecular  change, 
assuming  the  liquid  condition  ;  when  this  is  complete,  the 
temperature  again  commences  to  rise. 

That  we  may  have  precise  views  of  these  facts,  let  us 
suppose  that  the  mass  of  ice  and  the  warm  room  into 
which  it  is  carried  have  such  relations  to  each  other  that 
the  temperature  of  the  former  can  rise  from  the  zero  point 
one  degree  per  minute ;  for  thirty-two  minutes  the  tem- 
perature of  the  ice  will  be  found  to  increase,  and  at  the 
end  of  that  time,  a  thermometer,  if  applied,  would  stand 
at  32°.  But  now,  although  the  heat  is  still  entering  the 
ice  at  the  rate  of  a  degree  per  minute,  the  process  of 
warming  ceases,  and  for  140  minutes  no  farther  rise  takes 
place ;  the  ice  now  commences  to  melt,  and  in  140  min- 
utes the  liquefaction  is  complete.  The  temperature  then 
again  rises,  and  continues  to  do  so  with  regularity. 

We  infer  from  results  like  the  foregoing,  that  about 
140  degrees  of  heat  are  absorbed  by  ice  in  passing  into 
the  condition  of  water;  and  as  this  heat  is  not  discoverable 
by  the  thermometer,  it  is  designated  as  latent  heat. 

A  similar  fact  appears  when  any  liquid,  such  as  water, 
passes  into  the  gaseous  or  vaporous  condition.  Thus,  if 
some  water  be  exposed  to  a  fire  which  can  raise  its  tem- 
perature at  the  rate  of  one  degree  per  minute,  that  effect 
will  continue  until  212°  are  reached;  at  that  point,  no  mat- 
ter how  much  the  heat  be  increased,  the  temperature  re- 
mains stationary.  The  water  undergoes  a  change  of  form, 
assuming  the  condition  of  a  vapor,  and  the  change  is  com- 
pleted in  about  1000  minutes.  In  this,  as  in  the  former 
instance,  we  infer  that  a  large  amount  of  heat  has  become 
latent,  or  undiscoverable  by  the  thermometer,  and  that  it 
is  occupied  in  establishing  the  elastic  form  which  the 
water  has  assumed. 

Describe  the  change  which  ice  undergoes  when  warming.  Is  there  any 
pause  in  the  elevation  of  its  temperature  ?  How  many  degrees  of  heat 
are  absorbed  during  the  liquefaction  of  ice  ?  "What  is  latent  heat  ?  How 
many  degrees  of  heat  are  absorbed  during  the  vaporization  of  water? 
What  is  the  latent  heat  of  steam  I 


36  CALORIC    OF  FLUIDITY. 

The  caloric  which  thus  disappears  when  a  solid  as- 
sumes the  liquid  form,  takes  also  the  designation  of  caloric 
of  fluidity,  and  that  which  disappears  in  the  formation  of 
a  vapor,  the  caloric  of  elasticity. 

In  the  treatises  on  chemistry,  tables  may  be  found  ex- 
hibiting the  caloric  of  fluidity  of  different  bodies ;  thus, 
the  caloric  of  fluidity  of  water  is  140°,  that  of  melted  lead 
162°,  of  bees'  wax  175°,  and  of  melted  tin  500°. 

By  the  method  of  mixtures  the  same  results  may  be  es- 
tablished; thus,  if  a  pound  of  water  at  32°  is  mixed 
with  a  pound  at  172°,  the  mixture  will  have  the  mean 
temperature,  that  is,  102°;  but  if  a  pound  of  ice  at  32° 
be  mixed  with  a  pound  of  water  at  172°,  the  mixture  still 
remains  at  32°,  and  the  reason  is  clear,  from  the  foregoing 
considerations,  that  ice  in  passing  into  the  liquid  state  re- 
quires 140.°  of  caloric  of  fluidity  which  is  rendered  latent. 


LECTURE  IX. 

LATENT  HEAT.  —  Heat  evolved  in  Solidification.  —  Theory 
of  freezing  Mixtures.  —  Expansion  during  Solidification. 

—  Fixity  of  the  Melting  Point.  —  Latent  Heat  connected 
with  the  Duration  of  the  Seasons.  —  Nature  of  Vapors. 

—  Caloric  of  Elasticity. 


a  liquid  assumes  the  solid  form,  a  considerable 
amount  of  heat  is  evolved.     The  cause  is  readily  under- 
stood, from  what  we  have  seen  taking  place  during  the 
reverse  process;  which  has  led  us  to  the  fact  that  the 
Fig.  23.      difference  between  any  given  solid  and  the 
liquid  which  arises  from  it  by  melting  is  in 
the  large  amount  of  latent  heat  which  is  found 
in  the  latter,  and  which  is  occupied  in  giving 
it  its  form. 

A  saturated  solution  of  sulphate  of  soda 
may  be  cooled  from  its  boiling  point  to  com- 
mon temperatures,  in  a  vessel  tightly  corked, 
Lj  without  solidification  taking  place  ;  but  when 
the  cork  is  withdrawn  crystallization  ensues, 

What  is  caloric  of  fluidity  ?  What  is  caloric  of  elasticity  ?  How  can 
the  doctrine  of  latent  heat  be  established  by  the  .method  of  mixtures  ?  la 
heat  absorbed  or  evolved  when  a  liquid  solidifies  ?  What  is  the  cause  of 
this  ?  How  can  it  be  illustrated  with  a  solution  of  sulphate  of  soda  ? 


FREEZING    MIXTURES.  37 

and  heat  is  evolved.  This  may  be  proved  by  taking  a 
bottle,  a  a,  Fig.  23,  filled  with  such  a  solution  ;  and  having 
introduced  the  bulb  of  an  air  thermometer  through  the 
neck,  Z>,  by  means  of  an  air-tight  cork,  the  mouth,  c,  of 
the  bottle  is  to  be  .carefully  stopped.  When  the  whole 
apparatus  has  reached  the  ordinary  temperature  of  the 
air,  the  stopper  at  c  is  withdrawn,  and  solidification  at 
once  takes  place,  or,  if  it  should  at  first  fail,  the  introduc- 
tion of  a  crystal  of  sulphate  of  soda  will  bring  it  on.  At 
that  moment  it  will  be  perceived,  that  not  only  does  the 
thermometer  indicate  a  rise  of  temperature,  but  if  the  bot- 
tle be  grasped,  it  will  be  found  to  be  sensibly  warm. 

With  care,  water  may  be  cooled  to  a  point  far  below 
that  of  freezing  without  assuming  the  solid  form.  If,  un- 
der these  unusual  circumstances,  it  be  agitated,  solidifica- 
tion ensues,  and  heat  is  evolved,  the  temperature  rising  to 
32°. 

On  these  principles  depends  the  action  of  freezing  mix- 
tures, of  which  the  following  is  an  example  :  If  we  take 
eight  parts  of  crystallized  sulphate  of  soda,  and  mix  it  in  a 
thin  tumbler  with  five  parts  of  hydrochloric  acid,  the  sul- 
phate of  soda,  from  being  a  solid,  assumes  the  liquid  form  ; 
and  taking,  in  order  to  effect  that  change  of  form,  caloric 
from  surrounding  bodies,  it  reduces  their  temperature. 
This  may  be  shown  by  placing  four  parts  of  water  in  a 
thin  glass  test  tube,  and  stirring  it  about  in  the  mixture  ; 
the  water  speedily  freezes,  even  though  the  experiment 
may  be  made  on  a  warm  summer  day. 

In  the  treatises  on  chemistry  tables  of  freezing  mixtures 
are  inserted.  All  these  mixtures  depend  essentially  on 
the  principle  under  consideration — that  latent  heat  must 
be  furnished  to  a  substance  passing  from  the  solid  to  the 
liquid  state.  They  consist  of  various  solid  substances,  the 
liquefaction  of  which  is  brought  about  by  the  action  of 
other  bodies;  thus,  in  the  instance  we  have  seen,  the  sul- 
phate of  soda  is  brought  from  the  solid  to  the  liquid  state 
by  muriatic  acid,  and  heat  is  necessarily  absorbed.  Into 
the  composition  of  many  of  the  most  effective  of  these 
freezing  mixtures  ice  or  snow  enters.  Thus,  a  mixture 
of  snow  and  common  salt  will  bring  the  thermometer  be- 

Can  water  be  cooled  below  32°  without  freezing  ?  Give  an  example 
of  a  freezing  mixture.  What  are  the  principles  on  which  freezing  mix 
tures  act  ? 

D 


38  SOLIDIFICATION    OF    WATER. 

low  the  zero  point,  and  when  nitric  acid  is  poured  on 
gnow,  the  temperature  falls  as  low  as  thirty  degrees  be- 
low zero. 

Many  substances,  when  solidifying,  expand.  This  is  the 
case  with  water,  in  which  the  amount  of  expansion  is  about 
^th  of  the  bulk.  The  force  which  is  exerted  under  these 
circumstances  is  very  great,  and  capable  to  tearing  open 
the  strongest  vessels.  On  a  small  scale,  this  may  be  easily 
shown  by  filling  a  bottle  full  of  water,  and,  having  intro- 
duced the  cork,  fastening  it  tightly  down  with  a  piece  of 
wire.  On  putting  such  a  bottle  into  a  freezing  mixture, 
for  example,  snow  moistened  with  nitric  acid,  congelation 
promptly  takes  place,  and  the  bottle  is  burst. 

The  freezing  point  of  water  is  usually  spoken  of  as  a 
fixed  point,  and  is  marked  as  such  upon  the  scales  of  our 
thermometers  ;  but  if  water  be  cooled  without  allowing 
any  movement  or  agitation  of  its  parts,  it  may  be  brought 
as  low  as  15°.  It  is  then  in  the  same  condition  as  the 
saturated  solution  of  sulphate  of  soda  just  alluded  to. 
The  slightest  motion  is  sufficient  to  solidify  it.  But  though 
water  will  retain  its  liquid  form  far  below  its  freezing 
point,  ice  can  not  be  brought  above  32°  without  melting. 
The  melting  of  ice, k  and  not  the  freezing  of  water,  is  there- 
fore the  fixed  thermometric  point. 

We  have  seen  that  the  possession  of  a  point  of  maxi- 
mum density  by  water  exerts  a  great  effect  upon  the  du- 
ration of  the  seasons :  a  similar  observation  might  be  made 
as  respects  its  latent  heat.  If  ice,  by  the  absorption  of  a 
single  degree  of  heat,  when  it  passes  from  32°,  could 
turn  into  water,  the  great  deposits  of  winter  would  sud- 
denly melt,  and  inundations  be  frequent ;  or,  if  water,  by 
losing  a  single  degree  of  heat,  turned  into  ice,  freezing 
would  go  on  with  great  rapidity.  To  the  melting  of  ice, 
or  the  freezing  of  water,  time  is  necessary ;  the  140°  of 
latent  heat  have  to  be  disposed  of;  this,  therefore,  serves 
to  procrastinate  the  approach  of  winter,  and  causes  the 
spring  to  come  forward  with  more  measured  steps.  In 
autumn  the  water  has  140°  degrees  of  heat  to  give  out  to 

What  is  the  amount  of  the  expansion  of  water  in  the  act  of  freezing? 
How  may  the  force  with  which  this  expansion  takes  place  be  illustrated  ? 
Is  the  freezing  point  of  water  a  fixed  thermometric  point  ?  How  low  can 
water  be  cooled  without  freezing?  -Is  the  melting  of  ice,  or  the  freezing 
of  water,  the  fixed  thermometric  point  ?  What  connection  has  the  latent 
heat  of  water  with  the  duration  of  the  seasons  ? 


PROPERTIES    OF    VAPORS.  39 

surrounding  bodies  before  it  solidifies;  in  spring  it  must 
receive  the  same  amount  before  it  will  melt.  This,  there- 
fore, serves  as  a  check  upon  sudden  changes  in  the  seasons. 

Having  thus  discussed  the  leading  facts  observed  in  the 
change  from  the  solid  to  the  liquid  condition,  let  us  now 
;urn  our  attention  to  the  second  change  of  form,  the  pass- 
age from  the  liquid  to  the  gaseous  state. 

A  technical  distinction  is  made  between  a  gas  and  a 
vapor ;  by  the  latter,  we  understand  a  gas  which  will 
readily  take  on  the  liquid  form.  . 

Some  of  the  leading  peculiarities  in  the  constitution  of 
vapors  may  be  exhibited  by  the  following  pig.  24. 

experiment :  Take  a  glass  tube,  a  a,  Fig. 
24:,  with  a  bulb,  b,  blown  on  its  upper  ex- 
tremity ;  pour  water  into  the  bulb,  filling 
the  tube  to  within  an  inch  or  two  of  the 
end ;  this  vacant  space  fill  with  sulphuric 
ether ;  and  now,  closing  the  end  of  the  tube 
with  the  finger,  invert  it  in  a  glass  of  wa- 
ter, as  is  represented  in  the  figure.  The  ether,  being 
much  lighter  than  water,  at  once  rises  to  the  upper  part 
of  the  bulb,  as  is  shown  by  the  light  space,  the  bulb  being 
of  course  full  of  ether  and  water  conjointly. 

On  the  application  of  a  spirit  lamp  the  ether  vaporizes, 
and  presses  the  water  out  of  the  bulb  into  the  glass  cup. 
Three  important  facts  may  now  be  established. 

1st.  Vapors  occupy  more  space  than  the  liquids  from 
which  they  arise. 

2d.  They  have  not  a  misty  or  fog-like  appearance,  but 
are  perfectly  transparent. 

3d.  When  their  temperature  is  reduced,  they  collapse 
to  the  liquid  state. 

That  the  first  of  these  observations  is  true,  is  at  once 
seen  on  comparing  the  quantity  of  ether  with  the  volume 
of  vfypor  which  has  risen  from  it ;  the  ether  occupying  but 
a  small  space  at  the  top  of  the  bulb,  the  vapor  fills  it  en- 
tirely. We  perceive,  moreover,  that  ethereal  vapor  does 
not  possess  that  cloudy  appearance  which  is  popularly  at- 
tached to  the  term  vapor,  but  that  it  is  as  transparent  as 

What  is  the  distinction  between  a  gas  and  a  vapor  ?  Describe  the  ex- 
periment represented  in  Fig.  24.  What  is  the  difference  between  a  va- 
por and  the  liquid  which  forms  it,  as  to  volume  ?  Have  vapors  necessari- 
ly a  cloudy  appearance  ? 


40 


VAPORIZATION. 


atmospheric  air.  And,  on  removing  the  lamp,  so  that  the 
temperature  may  fall,  the  liquid  rushes  up  violently  into 
the  bulb,  exhibiting  the  ready  collapse  of  the  ether  vapor 
into  the  condition  of  a  liquid. 

We  have  already  proved  that  a  large  amount  of  heat 
becomes  latent,  constituting  the  caloric  of  elasticity  of  va- 
pors. The  temperature  of  steam  is  212°,  as  is  that  of  the 
water  from  which  it  rises  ;  but  it  contains  about  1000° 
of  latent  heat,  which  gives  to  it  its  new  form.  Different 
vapors  possess  different  quantities  of  latent  heat ;  thus,  for 
ether  the  number  is  163°,  for  alcohol  376°,  and,  as  we 
have  said,  for  water  1000°;  that  is  enough,  were  it  a 
solid,  to  make  it  visibly  red  hot  in  the  daylight. 


/  LECTURE  X. 

VAPORIZATION.  —  Vapors  form  at  all  Temperatures. — 
Form  instantly  in  a  Void. — Effects  of  removing  Pres- 
sure.— Measure  of  Elastic  Force  of  Vapors. —  Cumula- 
tive Pressure. — Failure  of '  Marriotte 's  Law. — Elasticity 
increases  with  Temperature^ — Maximum  Density  of  Va- 
pors. 

VAPORIZATION  goes  on  at  all  temperatures.  It  is  not 
Fig.  25.  necessary  that  the  boiling  point  should  be 
reached  ;  even  ice  will  evaporate  away.  The 
thin  films  of  this  substance  often  seen  incrust- 
ing  glass  windows  may  disappear  without  un- 
dergoing the  intermediate  process  of  fusion, 
and  a  mass  of  ice  freely  exposed  to  the  air  on 
a  dry,  frosty  day,  loses  weight.  Steam,  there- 
fore, rises  from  water  at  all  temperatures,  but 
with  more  rapidity  and  a  higher  elastic  force 
as  the  temperature  is  higher. 

In  a  vacuum  vapors  form  instantaneously. 
If  we  take  a  barometer,  a  a,  Fig.  25,  and 
pass  into  the  Torricellian  vacuum  which  ex 


On  reduction  of  the  temperature,  what  phenomenon  do  they  exhibit? 
How  are  these  three  facts  proved  ?  What  is  the  amount  of  caloric  of 
elasticity  of  steam  ?  Mention  it  also  in  the  case  of  ether  and  alcohol. 
How  can  it  be  proved  that  vaporization  goes  on  at  all  temperatures  ? 
"What  is  the  effect  which  ensues  when  a  vaporizable  liquid  is  passed  into 
a  Torricellian  vacuum  ? 


EFFECTS    OF    CHANGE    OF    PRESSURE.  41 

ists  at  its  upper  part,  a  small  quantity  of  sulphuric  ether, 
even  before  it  has  reached  the  void  space,  vapor  forms, 
and  the  mercury  is  instantly  depressed.  Under  ordinary 
circumstances,  when  the  instrument,  as  at  b  b,  is  standing 
at  30  inches,  the  column  at  once  falls  to  15  or  16,  the 
space  being  now  filled  with  the  vapor  of  ether ;  and  if  in 
succession  other  liquids  are  tried,  the  same  general  result 
is  obtained — instantaneous  vaporization  ;  but  the  amount 
of  vapor  set  free  is  different  in  the  different  cases. 

Diminution  of  atmospheric  pressure  is,  therefore,  favor- 
able to  vaporization,  and  were  the  pressure  of  the  air  en- 
tirely removed,  there  are  many  liquids  which  would  as- 
sume a  permanently  aerial  form.  Let  a,  Fig.  26,  be  a 
glass  bottle,  into  the  neck  of  which  a  funnel,  Fig_  26 
b  b,  is  ground  air-tight ;  the  bottle  is  to  be 
filled  with  quicksilver,  except  a  small  space 
at  its  upper  part,  which  is  occupied  by  sul- 
phuric ether.  If  this  instrument  be  placed 
beneath  the  receiver  of  an  air  pump,  as  soon 
as  exhaustion  is  made,  the  mercury  will  be 
seen  rising  into  the  funnel,  and  its  place  tak- 
en by  the  transparent  vapor  of  ether.  As 
long  as  the  reduction  of  pressure  continues, 
the  ether  keeps  the  gaseous  form,  but  on  re- 
admitting the  air,  it  returns  to  the  liquid 
state.  By  increase  of  pressure,  as  well  as  by  diminution 
of  temperature,  vapors  may  be  reduced  to  the  liquid  con- 
dition. 

Though  the  law  that  vapors  occupy  more  space  than 
the  liquids  from  which  they  come  is  of  universal  applica- 
tion, the  increase  of  volume  is  by  no  means  the  same  in 
all  cases.  Under  ordinary  circumstances  of  pressure,  a 
cubic  inch  of  water  at  its  boiling  point  produces  nearly  a 
cubic  foot  of  steam,  or  1696  cubic  inches,  more  accurate- 
ly. The  same  quantity  of  alcohol  produces  519  cubic 
inches,  and  of  oil  of  turpentine  192  cubic  inches. 

The  elastic  force  exerted  by  vapors  under  certain  lim- 
its can  be  measured  by  the  apparatus  given  in  Fig.  25. 
The  theory  of  the  process  is  very  simple.     The  height  at 
• 

What  substances  exist  commonly  in  the  liquid  state,  in  consequence  of 
the  pressure  of  the  air  ?  "What  is  the  effect  of  an  increased  pressure  on 
vapors  ?  Do  all  liquids  expand  equally  in  assuming  the  vaporous  state  ? 
How  can  the  elastic  force  of  vapors  be  measured  by  the  barometer  ? 

D  2 


42 


CUMULATIVE    PRESSURES. 


Fig.  27. 


which  the  barometer  stands  is  determined  by  the  pressure 
of  the  air.  In  the  experiment  there  described,  as  long  as 
there  is  nothing  to  counterbalance  that  pressure,  the  mer- 
cury is  forced  up  by  it  in  the  tube  to  a  height  of  30  inch- 
es ;  but  on  introducing  some  ether,  the  vapor  which 
forms,  exerting  an  elastic  forge  in  the  opposite  direction, 
tends  to  push  the  mercury  out  of  the  tube.  On  the  one 
hand,  we  have  the  pressure  of  the  air ;  on  the  other,  the 
elastic  force  of  the  ethereal  vapor;  they  press  in  opposite 
directions,  and  the  resulting  altitude  at  which  the  mercury 
stands  expresses,  and,  indeed,  measures  the  elastic  force 
of  the  vapor.  Thus,  at  a  temperature  of  eighty  degrees, 
water  will  depress  the  mercurial  column  about  1  inch,  al- 
cohol about  2  inches,  and  sulphuric  ether  about  20.  These 
numbers,  therefore,  represent  the  elastic  force  of  the  va- 
pors evolved. 

In  close  vessels,  from  which  there  is  no 
escape,  or  where  the  escape  is  greatly  re- 
tarded, a  constantly  accumulating  force  is 
generated,  when  the  temperature  is  raised. 
Thus,  if  we  place  some  water  in  a  flask, 
a,  Fig.  27,  into  which  a  tube,  b  b,  is  in- 
serted air-tight  by  means  of  a  cork,  and 
bent  in  the  form  exhibited  in  the  figure, 
and  dipping  nearly  to  the  bottom  of  the 
flask ;  on  the  application  of  a  spirit  lamp, 
the  vapor  .generated,  having  no  passage 
of  escape,  accumulates  in  the  upper  part  of  the  flask,  and, 
exerting  its  elastic  force,  presses  the 
liquid  through  the  tube  in  a  continu- 
ous stream.  The  mechanical  force 
which  thus  arises,  when  every  avenue 
of  escape  is  stopped,  is  strikingly  ex- 
hibited by  the  little  glass  bulbs  called 
candle  bombs ;  these  are  small  glob- 
ules of  glass,  about  as  large  as  a  pea, 
with  a  neck  an  inch  long ;  into  the  in- 
terior a  drop  of  water  is  introduced,  and  the  termination 
of  the  neck  hermetically  sealed  by  melting  the  glass. 
When  one  of  these  is  stuck  in  the  wick  of  a  candle  or 

What  is  the  principle  involved  ?  "When  -water  is  heated  in  a  vessel 
from  which  the  steam  can  not  escape,  what  is  the  effect  ?  How  may  this 
fr  *  illustrated  ? 


Fig.  28. 


RELATION    OF    VAPORS    TO    PRESSURE.  43 

0p,mp,  as  in  Fig.  28,  the  heat  vaporizes  f  a  portion  of  the 
water,  and  there  being  no  passage  through  which  the  steam 
can  escape,  the  bulb  is  burst  to  pieces  with  a  loud  explo- 
sion ;  a  mechanical  force  which  is  wonderful  when  we 
consider  the  amount  of  water  employed.  It  is  a  minia- 
ture representation  of  what  takes  place  on  the  large  scale 
in  the  bursting  of  high-pressure  steam-boilers. 

MARRIOTTE'S  law,  the  law  which  assigns  the  volume  of 
a  gas  under  variations  of  pressure,  applies,  under  certain 
restrictions,  to  the  case  of  vapors.  A  permanently  elas- 
tic gas,  when  the  pressure  is  doubled,  contracts  to  one  half 
of  its  former  volume ;  if  the  pressure  be  tripled,  to  one 
third,  and  so  on,  but  not  so  with  vapors;  if,  upon  steam, 
as  it  rises  from  water  at  212°,  any  increase  of  pressure 
be  exerted,  this  vapor  at  once  loses  its  elastic  form,  and 
instantly  condenses  into  water.  But  vapors,  like  atmo- 
spheric air,  if  the  pressure  upon  them  is  diminished,  fol- 
low Marriotte's  law ;  thus,  if  the  pressure  be  reduced  to 
one  half,  steam  at  once  doubles  its  volume.  For  vapors, 
therefore,  Marriotte's  law  holds  for  diminutions  of  press- 
ure, but  in  other  instances,  when  the  pressures  are  in- 
creased, it  apparently  fails,  the  vapors  relapsing  into  the 
liquid  form. 

That  the  elasticity  of  a  vapor  increases  with  its  temper- 
ature, may  be  readily  proved  by  taking  a  tube  one  Ft-.29. 
third  of  an  inch  in  diameter  and  12  inches  long, 
closed  at  one  end  and  open  at  the  other,  a  a,  Fig.  29, 
with  a  jar,  b,  an  inch  or  more  in  diameter  and  12 
inches  deep.  Let  the  tube  be  filled  with  quicksil- 
ver, so  as  to  leave  a  space  of  half  an  inch,  into  which 
ether  may  be  poured ;  invert  the  tube  in  the  deep 
jar,  also  containing  quicksilver;  the  ether  of  course 
rises  to  the  upper  closed  extremity.  If  now  the 
tube  be  lifted  in  the  jar  as  high  as  possible  without 

admitting  external  air,  a  certain  portion  of  the  ether     

will  vaporize,  and,  depressing  the  quicksilver,  its  elastic 
force  may  be  measured  by  the  length  of  the  resulting 
column.  If  now  the  end  of  the  tube  be  grasped  in  the 
hand,  or  if  it  be  slightly  warmed  by  the  application  of  a 

"What  is  Marriotte's  law  ?  Does  it  apply  in  the  case  of  vapors  under  a 
diminution  of  pressure?  Does  it  apply  under  an  increase?  What  rela- 
tion is  there  between  elasticity  and  temperature  ?  How  can  the  increase 
of  elastic  force  under  these  circumstances  be  shown? 


44  MEASURE    OF    ELASTIC    FORCE. 

lamp,  the  mercurial  column  is  at  once  depressed,  proving^ 
that  the  elastic  force  of  the  vapor  is  increasing.  As  soon 
as  the  tube  is  warmed  to  the  boiling  point  of  the  ether, 
the  column  of  mercury  is  depressed  exactly  to  the  level 
on  the  outside  of  the  tube.  At  this  point,  therefore,  it  bal- 
ances, or  is  equal  to  the  pressure  of  the  air. 

Now  let  the  tube  be  depressed  in  the  jar;  it  will  be 
seen  with  what  facility  the  vapor  reassumes  the  liquid 
condition.  As  the  tube  descends,  the  vapor  condenses, 
and  the  mercury  keeps  constantly  at  the  same  level. 

Under  these  circumstances,  it  follows  that  the  vapor 
is  at  its  maximum  density.  We  can  not  increase  that 
density  by  bringing  pressure  to  bear  upon  it  by  depress- 
ing the  tube,  for  the  moment  the  attempt  is  made  the 
vapor  liquefies. 


LECTURE  XL 

EBULLITION. —  Theory  of  Boiling. — In  Papin's  Digester 
Water  never  Boils. — Instantaneous  Condensation  of  Va- 
pors.— Effect  of  Variations  of  Pressure. — Effect  of  Na- 
ture of  the  Vessel. — Boiling  on  Mountains. — Effect  of 
Red-hot  Surfaces. 

BY  introducing  different  liquids  into  a  tube,  arranged 
as  that  represented  in  Fig. .29,  we  can  prove  that  the  ob- 
servation holds  good  in  every  case,  that,  as  soon  as  the 
boiling  point  of  a  liquid  is  reached,  the  elastic  force  of  the 
vapor  rising  from  it  is  equal  to  the  pressure  of  the  air. 

We  have  said  that  at  a  temperature  of  80°  the  vapor  of 
water  will  depress  the  mercurial  column  of  a  barometer 
about  one  inch,  but  if  the  temperature  be  raised  to  212°, 
the  mercury  is  at  once  depressed  to  the  level  in  the  cistern ; 
at  that  temperature,  therefore,  the  elastic  force  of  the 
vapor  is  equal  to  the  pressure  of  the  air. 

Upon  these  principles,  the  phenomena  of  boiling  or 
ebullition  are  easily  explained.  When  the  temperature 
of  a  liquid  is  raised  sufficiently  high,  vapor  is  rapidly  gen- 

At  the  boiling  point  of  a  liquid,  what  is  the  elastic  force  of  its  vapor 
equal  to  ?  What  is  meant  by  the  maximum  density  of  a  vapor  ?  How 
can  it  be  shown  that  vapors  thus  in  a  Torricellian  void  are  at  the  maxi- 
mum density  ?  At  the  boiling  point  of  water,  what  is  the  elastic  force  of 
its  steam  ?  Explain  the  phenomena  of  boiling. 


BOILING. 


45 


crated  from  those  portions  of  the  mass  which  are  hottest, 
and  the  violent  motion  characterized  by  the  term  "boiling" 
is  the  result.  This  is  due  to  the  fact  that  the  elastic  force 
of  the  generated  vapor  at  that  point  is  equal  to  the  at- 
mospheric pressure,  and  the  vapor  bubbles  expanding, 
can  maintain  themselves  in  the  liquid  without  being  crush- 
ed in ;  they  rise  to  the  surface,  and  there  burst.  But, 
just  before  ebullition  takes  place,  a  singing  sound  is  often 
heard,  due  to  the  partial  formation  of  bubbles,  which,  so 
long  as  they  are  in  the  neighborhood  of  the  hottest  part, 
have  elasticity  enough  to  maintain  their  form ;  but  the 
moment  they  attempt  to  rise  through  the  cooler  portion  of 
the  liquid  just  above,  their  elasticity  is  diminished  by 
their  decline  of  temperature,  and  the  atmospheric  pressure 
crushing  them  in,  they  resume  the  liquid  condition;  for 
a  few  moments,  therefore,  while  the  vapor  has  not  gath- 
ered elastic  force  enough  to  maintain  its  condition  per- 
fectly, these  bubbles  are  transiently  formed  and  disappear, 
and  the  liquid  is  thrown  into  a  vibratory  movement  which 
gives  rise  to  the  singing  sound. 

Water,  when  heated  in  a  vessel  from  which  the  steam 
can  not  escape,  never  boils.  This  takes  place  in  the  inte- 
rior of  Papin's  digester,  which  is  a  strong  metallic  vessel, 
in  which  water  is  enclosed,  and  the  orifice  through  which 
it  was  introduced  fastened  up.  As  the  steam  can  not  es- 
cape, the  water  can  not  boil,  no  matter  what  the  tempera- 
ture may  be.  But  the  vapor  which  accumulates  in  the  in- 
terior of  the  vessel  exerts  an  enormous  pressure.  It  is 
under  the  same  conditions  as  .were  considered  in  the  case 
of  the  candle  bombs.  Papin's  digest- 
er is  used  to  effect  the  solution  of  bod- 
ies by  water  which  are  not  acted  on 
readily  by  that  liquid  at  its  common 
boiling  point. 

As  a  vapor,  rising  from  a  vaporizing 
liquid,  will  bear  no  increase  of  press- 
ure, so  neither  will  it  bear  any  reduc- 
tion of  temperature  without  instanta- 
neously condensing.  This  may  be 
strikingly  shown  by  an  arrangement 


Fg.  30. 


What  is  the  cause  of  the  singing  sound  ?  Why  does  water  heated  in 
a  close  vessel  never  boil  ?  Describe  Papin's  digester.  What  is  its  use? 
Can  the  steam  of  boiling  water  be  cooled  without  condensation  ? 


46  RAPIDITY    OP    CONDENSATION. 

such  as  is  represented  in  Fig.  30.  Into  the  mouth  of  a 
flask,  «,  let  there  be  fitted  a  tube,  b,  half  an  inch  in  diam- 
eter, and  bent,  as  shown  in  the  figure.  Having  introduced 
a  little  water  into  the  flask,  cause  it  to  boil  rapidly  by  the 
application  of  a  spirit  lamp :  the  steam  which  forms  soon 
drives  out  the  atmospheric  air  from  the  flask  and  the 
tube,  and  when  this  is  entirely  completed,  and  the  vapor 
issuing  abundantly  from  the  mouth  of  the  tube,  plunge 
the  end  of  the  tube  beneath  some  cold  water  contained  in 
the  jar,  c,  and  take  away  the  lamp.  As  soon  as  this  is 
done,  the  cold  water,  condensing  the  steam  in  the  tube, 
rises  to  occupy  its  place  ;  and  presently  passing  over  the 
bend,  introduces  itself  with  surprising  violence  into  the 
interior  of  the  flask,  filling  it  entirely  full,  or,  which  more 
commonly  takes  place,  breaking  it  to  pieces  with  the  force 
of  the  shock.  The  low-pressure  steam-engine  depends  on 
this  fact  of  the  rapid  condensibility  of  vapor,  the  high- 
pressure  engine  on  its  elastic  force. 

Fig.  si.  The  principle  involved  in  the  action  of 

the  low-pressure  engine,  and  more  espe- 
cially that  form  of  it  which  was  the  inven- 
tion of  Newcomen,  is  well  illustrated  by 
the  instrument  represented  in  Fig.  31.  It 
consists  of  a  glass  tube,  blown  into  a  bulb 
at  its  lower  extremity.  In  the  bulb  some 
water  is  placed,  and  a  piston  slides,  with- 
out leakage,  in  the  tube.  On  holding  the 
bulb  in  the  flame  of  a  spirit  lamp,  steam  is 
generated,  and  the  piston  forced  upward. 
On  dipping  it  into  a  basin  of  cold  water, 
the  steam  condenses  and  the  piston  is  de- 
pressed ;  and  this  action  may  be  repeated 
at  pleasure. 

As  the  pressure  of  the  atmosphere  determines  the  boil- 
ing point  of  a  liquid,  and  as  that  pressure  is  variable,  the 
"boiling  point  is  not  a  fixed,  but  a  variable  point.  There 
are  many  experiments  which  might  be  introduced  as  proofa 
of  this  fact.  If  a  glass  of  warm  water  be  placed  beneath 
the  receiver  of  an  air  pump,  as  in  Fig.  32,  when  the 

Give  an  example  of  the  rapidity  of  its  condensation.  On  what  proper 
ty  of  vapor  does  the  low-pressure  steam-engine  depend  ?  On  what,  the 
h'igh-pressure  ?  How  may  it  be  proved  that  the  boiling  point  depends  on 
the  pressure  ? 


BOILING    IN    VACUO. 


47 


Fig.  32. 


rarefaction  has  reached  a  certain  point,  ebul- 
lition sets  in,  and  the  water  continues  to  boil 
at  a  lower  temperature  as  the  exhaustion  is 
more  perfect.  In  a  vacuum,  water  can  be 
made  to  boil  at  67°. 

On  this  principle,  that  the  boiling  point  de- 
pends on  the  existing  pressure,  we  give  an 
explanation  of  a  curious  experiment,  in 
which  ebullition  is  apparently  brought  about 
by  the  application  of  cold :  Take  a  Flor- 
ence flask,  a,  Fig.  33,  and,  having  filled 
it  half  full  of  water,  cause  the  water  to  b 
boil  violently,  so  as  to  expel  all  the  atmos- 
pheric air;  introduce  a  cork  which  will  fit 
the  mouth  of  the  flask  air-tight,  a  mo- 
ment after  it  is  moved  from  the  lamp,  and  before  any 
atmospheric  air  has  been  introduced.  If  the  flask  be 
now  dipped  into  a  jar,  b,  of  cold  water,  its  water  be- 
gins to  boil,  and  will  continue  to  do  so  until  its  tempera- 
ture is  reduced  quite  low.  The  cause  of  this  phenomenon 
is  due  to  the  fact,  that  the  cold  water  condenses  the  steam 
in  the  flask ,  and  a  partial  vacuum  is  the  result.  In  this 
partial  vacuum  the  water  boils,  as  in  the  experiment  il- 
lustrated by  Fig.  32;  and  the  steam,  as  fast  as  it  is  gen- 
erated, is  condensed  by  the  cold  sides  of  the  flask. 

Besides  this  variation  of  the  boiling  point  under  varia- 
tion of  pressure,  the  nature  of  the  vessel  in  which  the  pro- 
cess is  carried  forward  exerts  a  certain  action  ;  thus,  in  a 
polished  glass  vessel  the  boiling  point  is  214°,  but,  in  a 
rough  metal  vessel  it  is  212°. 

Some  travellers  report,  that  in  certain  mountainous  re- 
gions meat  can  not  be  cooked  by  the  ordinary  process  of 
boiling.  As  we  ascend  to  elevated  regions  in  the  air?  the 
atmospheric  pressure  becomes  less,  because  the  column 
of  air  above  is  shorter,  and  therefore  there  is  less  air  to 
press.  Under  such  circumstances,  the  boiling  point  of 
water  of  course  descends,  and  may  possibly  become  so 
low  as  to  be  unable  to  bring  about  the  specific  change  re- 
quired in  the  cooking  of  meat.  An  ascent  through  530 

At  what  temperature  will  water  boil  in  vacuo  ?  Explain  the  process 
by  which  warm  water  may  be  made  to  boil  by  the  application  of  cold  ? 
How  does  the  nature  of  the  vessel  affect  the  boiling'  point  ?  Why  is  it 
probable  that  meat  can  not  be  cooked  on  high  mountains  ? 


48  LIQUIDS    ON    RED-HOT    SURFACES. 

feet  lowers  the  boiling  point  one  degree.  Upon  this  prin- 
ciple we  can  determine  the  altitude  of  accessible  eleva- 
tions, by  determining  the  thermometric  point  at  which 
water  boils  upon  them.  A  peculiar  thermometer,  called 
the  hypsometer,  has  been  invented  for  this  purpose. 

When  a  drop  of  water  is  placed  on  a  red-hot  polished 
surface  of  platinum,  it  does  not,  as  might  be  expected, 
commence  to  boil  rapidly,  but  remains  perfectly  quiescent, 
gathering  itself  up  into  a  globule.  If  the  platinum  be 
now  allowed  to  cool,  as  soon  as  its  temperature  has  reach- 
ed a  point  at  which  it  ceases  to  be  visibly  hot,  the  drop 
of  water  is  suddenly  dissipated  in  a  burst  of  steam. 
The  explanation  given  of  this  phenomenon  is,  that  at  the 
high  temperature  the  drop  is  not  fairly  in  contact  with  the 
red-hot  surface,  but  a  stratum  of  steam  intervenes ;  this, 
being  a  bad  conductor,  prevents  ebullition  from  occurring, 
but  as  soon  as  the  temperature  declines,  and  this  steam 
no  longer  props  up  the  drop,  an  explosive  ebullition  en- 
sues, because  of  the  contact  which  has  taken  place. 


LECTURE  XII. 

VAPORIZATION. —  The  Boiling  Point  rises  with  the  Press- 
ure.— Relation  between  sensible  and  insensible  Heat.— 
The  Cryophorus. — Leslie's  Process  for  freezing  Water. 
—  Variability  of  Moisture  in  the  Air. — Hygrometers. — 
Method  of  the  Dew  Point. 

UNDER  an  increase  of  pressure,  the  boiling  point  rises, 
and  the  elastic  force  of  the  steam  evolved  becomes  corre- 
spondingly greater.  As  we  have  seen,  the  elastic  force  of 
steam  from  water  boiling  at  212°  is  equal  to  the  press- 
ure of  one  atmosphere;  but  if  the  pressure  be  doubled, 
the  "boiling  point  rises  to  250°  ;  if  quadrupled,  to  294°  ; 
and  under  a  pressure  of  fifty  atmospheres,  it  is  more  than 
500°. 

How  high  must  we  ascend  to  bring  the  boiling  point  to  21 1°  ?  How 
may  the  altitude  of  mountains  be  determined  by  the  thermometer? 
"What  are  the  phenomena  exhibited  by  water  in  contact  with  red-hot 
platinum?  What  is  the  supposed  explanation?  .How  is  the  boiling 
point  affected  by  an  increased  pressure  ? 


LATENT  HEAT  OF  VAPORS.  49 

These  results  may  be  established  by  the  Fis-  24- 
aid  of  the  boiler,  represented  in  Fig.  34, 
<z.  It  is  a  globular  vessel  of  brass,  and  is 
about  three  inches  in  diameter.  In  its  up- 
per part  are  three  perforations,  into  one  of 
which  the  stop-cock,  b,  is  screwed  ;  through 
the  second  a  tube,  c,  is  inserted ,  deep  enough 
to  reach  nearly  to  the  bottom  of  the  boiler ; 
and  through  the  third  a  thermometer,  *d,  is 
introduced.  Some  quicksilver  is  poured 
in,  sufficient  to  cover  the  end  of  the  tube, 
c,  half  an  inch  or  more  deep,  and  upon  it 
water  is  poured,  the  bulb  of  the  thermometer  being  im- 
mersed in  it.  The  sto«,-cock,  b,  being  open,  a  spirit  lamp 
is  applied  to  bring  the  water  to  its  boiling  point,  and  as 
the  steam  can  freely  pass  out,  this  of  course  takes  place 
at  212°.  On  closing  the  stop-cock,  the  steam  can  no  lon- 
ger escape,  but  exerting  its  elastic  force  on  the  surface  of 
the  boiling  liquid,  presses  the  mercury  up  in  the  tube,  c. 
The  altitude  of  the  mercurial  column  measures  the  amount 
of  this  pressure,  and  the  thermometer  indicates  the  corre- 
sponding change  in  the  boiling  point:  as  soon  as  the  press- 
ure is  equal  to  two  atmospheres,  the  thermometer  will 
be  found  to  have  risen  to  250°. 

It  is  immaterial  at  what  temperature  vaporization  is 
carried  on,  a  very  large  amount  of  heat  must  always  be 
rendered  latent ;  and,  in  point  of  fact,  vapors  generated  at 
a  low  temperature  contain  more  latent  heat  than  those 
generated  at  a  high  one.  The  relation  which  exists  in 
the  amount  of  heat  rendered  latent  at  different  tempera- 
tures is  very  simple.  The  sum  of  the  insensible  and 
sensible  heat  is  always  the  same ;  thus,  water  boiling  at 
212°  absorbs  1000°  of  latent  heat,  the  sum  of  the  two 
quantities  being  of  course  1212° ;  but  vapor  rising  from 
water  at  32°  contains  of  latent  heat  1180°  ;  here,  again, 
the  sum  of  the  two  quantities  is  1212°  ;  and  the  same  ob 
servation  holds  for  intermediate  temperatures. 

When  vapors  return  to  the  liquid  condition,  the  heat 
which  has  been  latent  in  them  reassumes  the  sensible 


Describe  the  boiler,  Fig.  34,  and  its  use.  Do  vapors  generated  at  low 
or  high  temperatures  contain  most  latent  heat  ?  What  relation  is  there 
between  the  insensible  and  sensible  heats  of  vapors  at  different  tempera 
tures  ?  When  a  vapor  condenses,  what  becomes  of  its  latent  heat  ? 

E 


50  THE    CRYOPHORUS. 

form.  They  may  thus  be  regarded  as  containing  a  great 
store  of  caloric,  of  the  effects  of  which  many  natural  phe- 
nomena furnish  us  with  striking  examples.  Thus,  there 
is  a  remarkable  difference  between  the  climate  of  the 
eastern  coast  of  America  and  the  opposite  European 
coasts  in  the  same  latitude,  and  this  arises  from  the  action 
of  the  Gulf  Stream,  a  great  stream  of  warm  water,  which, 
issuing  from  the  Gjjlf  of  Mexico,  and  passing  the  Atlantic 
States,  stretches  across  toward  the  European  Continent. 
The  vapors  which  arise  from  it  give  forth  their  latent  heat 
to  the  air,  and  the  southwest  winds,  which  are  therefore 
damp  and  warm,  moderate  the  climates  of  those  coun- 
tries. 

The  cryophorus,  or  frost  bearer,  an  instrument  invent- 
Fig.  35  e(^  by  Dr.  Wollaston,  in  which  water  may  be 
frozen  by  the  cold  produced  by  its  own  evapo- 
ration, depends  for  its  action  on  the  laws  re- 
lating to  latent  heat.  It  is  represented  in  Fig. 
35,  and  consists  of  a  bent  tube,  c,  half  an  inch 
or  more  in  diameter,  with  a  bulb,  a  and  3,  at 
each  of  its  extremities ;  the  upper  bulb,  b,  is 
filled  one  third  with  water,  and  the  rest  of 
the  space,  with  the  tube,  c,  and  the  other  bulb, 
a,  is  free  from  atmospheric  air,  and  occupied  by 
the  vapor  of  water  only.  If,  now,  the  bulb  a  be 
immersed  in  a  freezing  mixture  of  nitric  acid  and  snow, 
although  the  tube,  c,  may  be  of  considerable  length,  the 
water  in  the  distant  bulb,  5,  presently  freezes ;  hence  the 
name  of  the  instrument,  frost  bearer,  because  cold  applied 
at  one  point  produces  a  freezing  effect  at  another,  which 
is  at  a  considerable  distance.  The  action  of  the  instrument 
is  simple  :  in  the  cold  bulb,  <z,  which  is  in  contact  with 
the  freezing  mixture,  the  vapor  is  condensed;  fresh  quan- 
tities rise  with  rapidity  from  the  water  in  the  other  bulb, 
to  be  in  their  turn  condensed;  a  continual  condensation, 
therefore,  goes  on  in  c,  and  a  continual  evaporation  in  b, 
but  the  vapor  thus  formed  in  b  must  have  caloric  of  elas- 
ticity ;  it  obtains  it  from  the  water  from  which  it  is  rising, 
the  temperature  of  which  therefore  descends  until  solidi- 
fication takes  place. 

What  effect  has  the  Gulf  Stream  on  the  climate  of  Europe  ?  Explain 
the  cause  of  it.  Describe  the  cryophorus.  What  is  the  reason  that  cole1 
applied  to  one  bulb  freezes  -water  in  the  other  ? 


HYGROMETERS.  51 

Leslie's  process  for  freezing  water  in  vacuo  by  its  own 
evaporation  is  an  example  of  the  same  kind.  If  some 
water  in  a  watch-glass  is  placed  in  an  exhausted  receiver, 
with  a  large  surface  of  sulphuric  acid,  as  fast  as  vapoi 
rises  it  is  condensed  by  the  acid ;  a  rapid  Figf  35. 

evaporation  of  the  water  therefore  takes 
place,  the  temperature  falls,  and  congela- 
tion finally  ensues.  In  Fig.  36  this  ap- 
paratus is  represented :  a  is  the  Watch- 
glass  containing  water,  b  a  wide  dish 
filled  with  sulphuric  acid,  and  c  a  low  bell  jar  in  which 
the  exhaustion  is  made. 

A  drop  of  prussic  acid  held  in  the  air  on  the  tip  of  a  rod 
solidifies,  the  portion  that  evaporates  obtaining  its  latent 
heat  from  the  portion  left  behind,  and  on  the  same  prin- 
ciple liquid  carbonic  acid  can  also  be  solidified. 

The  amount  of  watery  vapor  contained  in  the  air  is 
very  variable.  Many  common  facts  prove  this  :  the  swell- 
ing of  wooden  furniture  takes  place  in  consequence  of 
damp  weather ;  and  the  opposite  effect,  or  its  shrinking, 
occurs  during  dry.  Several  instruments  have  been  invent- 
ed to  determine  what  the  amount  is  at  any  time ;  they 
are  called  hygrometers.  In  one  of  these,  the  relative  damp- 
ness or  dryness  of  the  atmosphere  is  determined  by  the 
stretching  or  contracting  of  a  hair,  which  is  very  sensitive 
to  such  changes.  A  general  idea  of  such  an  instrument 
may  be  obtained  by  considering  the  metallic  bar  of  the 
pyrometer,  Fig.  15,  to  be  replaced  by  a  hair,  the  move- 
ments of  which  would  of  course  be  communicated  to  the 
index  ;  in  another  a  slip  of  whalebone  is  used  instead  of 
the  hair.  There  is  a  simple  and  ingenious  instrument, 
the  movements  of  which  depend  on  these  principles  ;  it  is 
represented  in  Fig.  37  :  a  thin  slip  Figf  37 

of  pine   wood,  a  a,  cut   across  the      JL^^^      ^.m. JL 

grain,  a  foot  long  and  an  inch  wide,    /V:   "     •  •  •  • -v~s> 

has    inserted   into  its    corners   four 

needtes,  all  pointing  in  one  direction  backward  ;  if  this 
instrument  be  set  upon  a  floor  or  flat  table,  in  the  course 
of  time  it  will  crawl  a  considerable  distance.  During  dry 

Describe  Leslie's  process  for  freezing  water  in  vacuo  ?  Why  does  a 
drop  of  prussic  acid  held  in  the  air  solidify  ?  How  can  it  be  proved  that 
the  amount  of  moisture  in  the  air  is  variable  ?  What  is  the  hygrometer  ? 
Describe  the  hair  hygrometer.  Describe  the  instrument,  Fig.  37- 


THE    DEW    POINT. 


weather  the  thin  board  contracts,  and  the  two  fore  legs 
taking  hold  of  the  table,  the  hind  ones  are  drawn  up  a 
little  space  ;  when  the  weather  turns  damp,  the  board  ex- 
pands, and  now  the  hind  legs  pressing  against  the  table, 
cause  the  fore  ones  to  advance.  Every  change  from  dry 
to,  damp,  or  the  reverse,  produces  a  walking  motion  in  a 
continuous  direction,  and  the  distance  passed  over  is  a 
register  of  the  sum  total  of  these  changes. 

But  of  all  these  hygrometric  methods,  the  process 
known  as  "  the  determination  of  the  dew  point"  is  by  far 
the  most  philosophical.  This  method  consists  in  cooling 
the  air  until  it  begins  to  deposit  moisture.  When  there  is 
much  moisture  in  the  air,  it  obviously  requires  but  a  slight 
diminution  of  temperature  to  cause  a  portion  of  the  vapor 
to  deposit  as  a  dew ;  but  when  the  air  is  dryer,  the  cool- 
ing must  be  carried  to  a  greater  extent.  The  precise 
thermometric  point  .at  which  the  moisture  begins  to  de- 
posit is  called  the  dew  point. 

Thus,  if  we  take  a  thin  metallic  vessel  containing  water, 
and  cool  it  gradually  by  the  addition  of  a  mixture  of 
nitrate  of  potash  and  sal  ammoniac,  or  any  of  the  cooling 
mixtures,  continually  stirring  with  the  bulb  of  a  small 
thermometer,  as  soon  as  the  temperature  has  reached  a 
Fig.  38.  certain  point  a  dew  is 

deposited  on  the  outside 
of  the  metallic  vessel ; 
that  temperature  is  the 
dew  point  for  the  time 
being.  Knowing  the  tem- 
perature of  the  air,  the 
dew  point,  and  the  baro- 
metric pressure,  the  abso- 
lute amount  of  vapor  can 
be  determined  by  a  sim- 
ple calculation. 

Daniell's  hygrometer 
affords  a  ready  and  beau- 
tiful method  of  determin- 
ing the  dew  point.  It 
consists  of  a  cryophorus, 
a  c  I,  Fig.  38,  the  bulb 

What  is  meant  by  the  "  dew  point  ?''     "What  is  the  process  for  ascer- 
taining it  ?     Describe  Daniel!  's  hygrometer  and  the  mode  of  using  it. 


SPECIFIC    GRAVITY    OF    VAPORS. 


53 


b  being  made  of  black  glass,  and  a  covered  over  with 
muslin.  The  bulb  b  contains  ether  instead  of  water,  and 
into  it  there  dips  a  very  delicate  thermometer,  d.  Usually, 
another  thermometer  is  affixed  to  the  stand  of  the  instru- 
ment. When  a  little  ether  is  poured  on  a,  by  its  evapo- 
ration it  cools  that  bulb,  and  ether  distils  over  from  b, 
which,  of  course,  also  becomes  cold.  After  a  time,  the 
temperature  of  b  sinks  to  the  dew  point,  and  that  bulb 
becomes  covered  with  a  mist.  The  thermometer,  d,  then 
shows  at  what  temperature  this  takes  place,  and  of  course 
gives  the  dew  point. 


LECTURE  XIII. 

EVAPORATION  AND  INTERSTITIAL  RADIATION. — Methods 
of  Gay-Lussac  and  Dumas  for  ascertaining  the  Specific 
Gravity  of  Vapors. — Phenomena  of  Evaporation. — 
Control  of  Temperature. — Effect  of  Dryness,  Stillness, 
Pressure,  and  Surface. — Evaporation  a  Cooling  Pro- 
cess.— Conduction  of  Solids. — Difference  among  different 
Metals. — Rumford's  Experiments. 

THE  specific  gravity  of  vapors  may  be  de-  Fig.  39. 
termined  in  several  ways.  The  following  is 
the  method  of  Gay-Lussac  :  A  graduated  jar, 
a,  is  inverted  in  a  basin  of  mercury,  c,  which 
rests  upon  a  small  furnace.  A  glass  bulb  is  to 
be  filled  quite  full  with  the  liquid  under  ex- 
amination, and  the  quantity  introduced  is  accu- 
rately weighed.  The  bulb  is  now  slipped  into 
the  jar,  a,  and  rises  to  its  top.  A  cylinder,  b, 
open  at  both  ends,  but  the  lower  pressed  down 
into  the  mercury,  is  next  placed  round  a,  and 
the  interval  filled  with  clear  oil.  The  furnace 
is  now  lighted  ;  the  oil  and  the  mercury  be- 
come warm  ;  the  bulb  at  last  bursts,  and,  as  its 
vapor  depresses  the  mercury  in  the  graduated  jar,  its  vol- 
ume may  be  determined.  Thus,  knowing  the  weight  of 
the  liquid,  the  volume  of  its  vapor,  and  the  temperature 

Describe  Gay-Lussac's  method  of  determining  the  specific  gravity  of  a 
vapor. 


54 


SPECIFIC    GRAVITY    OF    VAPORS. 


of  the  oil,  we  can  easily  calculate  the  volume  at  32°,  and 
from  that  deduce  the  specific  gravity. 

The  method  of  Dumas  consists  in  weighing  a  glass  globe 
Fig.  40.  filled  with  the 

vapor  to  be 
tried.  A  por- 
tion of  the  sub- 
stance is  to  be 
introduced  in- 
to the  globe, 
the  weight  of 
which  is  first 
determined, 
and  this  is  then 
held,  as  shown 
in  the  figure,  in 
a  bath  of  fusi- 
ble metal  pla- 
ced over  a  small  furnace.  The  heat  of  the  melted  metal 
vaporizes  the  substance,  drives  out  the  air,  and  occupies 
the  whole  cavity  in  a  state  of  purity.  When  no  more 
vapor  escapes  from  the  end  of  the  tube  it  is  sealed  by  the 
blow-pipe,  and  the  temperature  of  the  bath  ascertained. 
The  globe  is  now  to  be  carefully  weighed,  when  cold,  a 
second  time,  and  the  point  of  the  tube  is  then  broken  un- 
der quicksilver,  which  rises  and  fills  it  completely,  and 
this  being  subsequently  emptied  into  a  graduated  jar,  the 
volume  of  the  globe  is  ascertained.  Knowing  the  vol- 
ume of  the  globe,  we  know  the  weight  of  the  air  it  con- 
tains, and  this,  subtracted  from  the  first  weight,  is  the 
weight  of  the  glass  when  empty.  Subtracting  this  again 
from  the  second  weighing,  gives  us  the  weight  of  the  va- 
por, and  as  the  air  and  the  vapor  occupied  the  same  vol- 
ume, their  densities  are  as  their  weights.  But,  as  their 
temperature  was  different,  a  farther  calculation  is  required 
to  bring  them  to  the  same  standard. 

There  are  several  conditions  which  exert  a  control 
over  the  lapidity  of  evaporation.  The  amount  of  vapor 
which  can  exist  in  a  given  space  depends  entirely  on  the 
temperature.  Thus  the  air  included  in  a  glass  jar  which 
is  standing  over  water  contains,  at  32°,  a  certain  quantity 

Describe  the  method  of  Dumas.    What  is  it  that  regulates  the  quantity 
of  vapor  in  a  given  space  ? 


CAUSES    CONTROLLING    EVAPORATION.  55 

of  vapor  ;  but  if  the  temperature  rises  to  60°,  it  contains 
more,  and  still  more  if  it  rises  to  90°.  Should  the  tem- 
perature descend,  a  part  of  the  vapor  is  deposited  as  a 
mist.  The  quantity  that  remains  in  suspension  is  determ- 
ined by  the  temperature  alone. 

It  is  the  application  of  this  principle  which  constitutes 
the  most  beautiful  part  of  Watts's  great  invention,  the 
low-pressure  steam-engine.  Taking  advantage  of  the 
fact  that  the  quantity  of  vapor  which  can  exist  in  a  given 
space  is  determined  by  the  lowness  of  temperature  of  any 
portion  of  it,  he  arranged  a  vessel,  maintained  uniformly 
at  a  low  temperature,  in  connection  with  the  cylinder  of 
the  engine,  and  thus  reached  the  apparently  paradoxical 
result  of  condensing  the  steam  without  cooling  the  cyl- 
inder. 

Among  other  causes  exerting  a  control  over  evapora- 
tion in  the  air  is  the  dry  or  damp  state  of  that  medium. 
As  is  well  known,  evaporation  goes  on  with  rapidity  when 
the  weather  is  dry,  and  is  greatly  retarded  when  the 
weather  is  damp.  So,  too,  a  movement  or  current  exerts 
a  great  effect.  When  the  wind  is  blowing,  water  will 
evaporate  much  more  quickly  than  when  the  air  is  quite 
calm ;  this  obviously  depends  on  a  constant  renewal  of 
surfaces,  so  that  as  fast  as  one  portion  of  air  becomes 
moist  it  is  removed,  and  a  dryer  portion  takes  its  place. 
Extent  of  surface  operates  in  the  same  way  ;  the  same 
quantity  of  water  will  evaporate  much  more  rapidly  if 
exposed  in  a  plate  than  if  exposed  in  a  cup.  Pressure 
also  exerts  a  great  control ;  for,  as  we  have  seen,  evap- 
oration takes  place  instantaneously  in  a  vacuum. 

While,  therefore,  there  are  several  circumstances  which 
can  control  the  rate  of  evaporation,  it  is  temperature  alone 
which  regulates  the  absolute  and  final  amount.  As  we 
have  just  seen,  a  fixed  quantity  of  vapor  can  exist  in  a 
certain  space  at  a  given  temperature ;  and  it  matters  not 
whether  that  space  is  full  of  atmospheric  air  or  is  a  vacu- 
um, the  absolute  quantity  will  be  precisely  the  same. 

At  one  time  it  was  supposed  that  evaporation  was  due 
lo  a  solvent  power  in  the  air — a  kind  of  attraction  be- 
tween that  medium  and  the  water  with  which  it  is  in  con- 
On  what  principle  does  the  steam-engine  condenser  depend?  What 
effect  have  dryness  or  dampness  over  evaporation  ?  "What  is  the  effect 
of  a  current  ?  What  of  extent  of  surface  ?  What  of  pressure  ?  What 
of  temperature  ? 


56  EVAPORATION    IS    A    COOLING    PROCESS. 

tact ;  but  it  is  clear  that  such  an  opinion  is  wholly  untena 
ble,  for  the  process  goes  forward  with  the  greatest  rapid- 
ity in  a  vacuum,  when  the  air  is  totally  removed. 

Although  the  evaporation  of  liquids,  such  as  water,  will 
take  place  at  very  low  temperatures,  there  is  reason  to  be- 
lieve that  the  process  has  a  limit;  thus,  a  minute  quantity 
of  vapor  will  rise  from  quicksilver  at  a  temperature  of 
60°,  but  at  40°  not  a  trace  can  be  discovered. 

All  processes  of  evaporation  are  cooling  processes,  be- 
cause the  vapor  developed  requires  latent  heat  to  give  it 
the  elastic  form.  For  this  reason,  when  any  vaporizable 
liquid,  as  ether,  is  poured  on  the  bulb  of  an  air  thermom- 
eter, or  on  the  hand,  cold  is  produced. 

Fig.  41.  The  pulse  glass  ig  an  instru- 

ment which  may  serve  as  an 
illustration  :  it  consists  of  $ 
glass  tube,  bent  twice  at  right 
angles,  and  terminated  by 
bulbs,  as  in  Fig.  41.  It  is  partially  filled  with  spirit  of 
wine,  the  rest  being  occupied  by  the  vapor  of  that  sub- 
stance. On  grasping  one  of  the  bulbs  in  the  hand,  the 
warmth  is  sufficient  to  boil  the  liquid  ;  and  as  it  distills 
over  into  the  other  bulb,  an  impression  of  cold  is  felt. 

We  now  come  to  the  consideration  of  the  mode  by 
which  heat  is  transmitted  through  bodies,  or  interstitial 
radiation,  called  by  many  writers  conduction  ;  a  term  in- 
volving the  idea  that  the  particles  of  bodies  are  in  actual 
contact,  whereas  it  has  been  abundantly  proved  that  they 
are  separated  from  each  other  by  interstices.  The  pass- 
age of  the  heat  across  these  spaces  is  what  is  meant  by  in- 
terstitial radiation.  From  the  currency  which  it  has  ob- 
tained, and  the  convenience  of  the  expression,  I  shall  con- 
tinue to  use  the  word  conduction. 

Different  solids  conduct  heat  with  different  degrees  of 
facility.  If  we  take  a  cylindrical  mass  of  metal,  and  hold 
tightly  against  its  surface  a  piece  of  white  writing  paper, 
the  paper  may  be  placed  in  the  flame  of  a  spirit  lamp  for 
a  considerable  time  without  scorching ;  but  if  we  take  a 
cylindrical  piece  of  wood  of  the  same  dimensions,  and, 

Does  evaporation  arise  from  a  solvent  power  in  the  air  ?  Is  there  any 
limit  to  evaporation?  Why  are  processes  of  evaporation  cooling  pro- 
cesses ?  Describe  the  pulse  glass.  What  is  interstitial  radiation  ?  What 
is  conduction?  How  may  it  be  proved  that  wood  and  metals  conduct 
with  different  degrees  of  facility  ? 


CONDUCTION    OF    KEAT.  57 

wrapping  the  paper  round  it,  expose  it  to  the  flame,  it 
rapidly  scorches.  The  metal,  therefore,  keeps  the  paper 
cool  by  carrying  off  its  heat,  but  the  wood,  being  a  bad 
conductor,  suffers  the  paper  to  burn. 

By  the  aid  of  the  apparatus  of  Ingenhouse,  Fig.  42,  the 
same  fact  may  be  proved  in  a  more  gen-  Fig.vz. 

oral  way.  It  consists  of  a  trough  of  brass, 
six  inches  or  more  long,  three  wide,  and 
three  deep  ;  from  the  front  of  it  project 
cylinders  of  metallic  and  other  substances 
of  the  same  length  and  character ;  they 
may  be  of  silver,  copper,  brass,  iron,  porcelain,  wood,  &c., 
in  succession ;  the  surface  of  each  cylinder  is  smeared 
with  bees'  wax.  On  pouring  boiling  water  into  the  trough, 
the  heat  passes  along  these  cylinders  with  a  rapidity  cor- 
responding to  their  conducting  power,  and  the  wax  cor- 
respondingly melts.  On  the  silver  bar  the  wax  melts 
most  rapidly,  and  on  the  wood  most  slowly :  on  the  others 
intermediately  ;  thus  affording  a  clear  proof  that  different 
solids  conduct  heat  with  different  degrees  of  facility. 

Even  among  metallic  substances,  great  differences  in 
this  respect  exist,  as  may  be  strikingly  Fig.  43. 

shown  by  the  instrument,  Fig.  43.  Into 
a  solid  ball  of  copper,  a,  three  wires  of 
equal  length  and  equal  diameter  are 
screwed — they  may  be  copper,  brass,  and 
iron,  respectively  :  they  are  flattened  at 
their  farther  extremities,  b,  c,  d,  so  as  to  af- 
ford a  place  on  which  pieces  of  phospho- 
rus  may  be  put.  A  lighted  spirit  lamp  is 
now  set  beneath  the  central  ball,  the  temperature  of  which 
soon  rises,  and  the  heat  passes  with  different  degrees  of 
speed  along  the  metals;  very  soon  the  piece  of  phosphorus 
at  the  end  of  the  copper  takes  fire  ;  then,  some  time  after, 
follows  that  on  the  brass  ;  and  last,  that  on  the  iron ;  en- 
abling us  to  prove  to  persons  at  a  distance  the  fact  that 
these  different  metals  conduct  heat  with  different  degrees 
of  facility. 

If  a  piece  of  wire  gauze  be  held  over  the  flame  of  a  candle 
or  gas  jet,  Fig.  44,  the  flame  fails  to  pass  through  ;  but  the 

Describe  the  apparatus  of  Ingenhouse  ?  "What  does  it  prove  ?  Are 
there  differences  in  the  conducting  powers  of  metals  ?  How  may  that  bo 
paoved  1 


58 


CONDUCTING    POWER    OF    METALS. 


.  45. 


Fig.  44.  gaseous  matter  of  which  the  flame  consists 

freely  escapes  through  the  meshes  of  the 
gauze,  for  it  may  be  set  on  fire,  as  shown  in 
the  figure.  Flame  is  gaseous  matter,  or 
solid  matter  in  a  state  of  excessive  sub- 
division, temporarily  suspended  in  gas, 
brought  to  a  very  high  temperature.  It 
can  not,  therefore,  pass  through  a  piece  of 
wire  gauze,  because  the  metallic  threads, 
exerting  a  high  conducting  power,  ab- 
stract its  heat  from  the  incandescent  gas, 
and  bring  its  temperature  down  to  a  point  at  which  it  ceas- 
es to  be  luminous.  The  safety-lamp  of  Davy  is  an  appli 
cation  of  this  principle  ;  by  it  combustion  is  prevent- 
ed  from  spreading  through  masses  of  explo- 
sive gas,  by  calling  into  action  the  conduct- 
ing power  of  a  metallic  gauze,  with  which  the 
lamp  flame  i.s  surrounded,  as  in  Fig.  45.  The 
safety-tube  of  Hemmings,  used  to  prevent  ex- 
plosions in  the  oxyhydrogen  blow-pipe,  acts  on 
the  same  principle. 

Count  Rumford  made  several  experiments  to 
determine  the  conducting  power  of  those  vari- 
ous materials  which  are  used  for  the  purpose  of 
clothing.  He  placed  the  bulb  of  a  thermometer 
in  the  center  of  a  spherical  glass  globe  of  lar- 
ger diameter,  and  filled  the  interspace  with  the 
substances  to  be  tried.  Having  immersed  the 
apparatus  iri  boih'ng  water  until  it  was  at  212°, 
he  transferred  it  to  melting  snow,  and  ascertain- 
ed how  long  it  took  to  fall  a  given  number  of  degrees. 
Linen  and  cotton  were  found  to  be  better  conductors 
than  wool  and  the  various  furs,  and  hence  the  reason  that 
they  are  preferred  as  articles  of  summer  clothing  ;  but 
he  also  found  that  much  depended  on  the  tightness 
with  which  the  substances  were  packed,  for  the  conduct- 
ing power  apparently  rose  when  they  were  closely  com- 
pressed. These  bodies  act,  therefore,  as  will  hereafter 


Can  the  flame  of  a  candle  pass  through  a  piece  of  wire  gauze  ? 
is  the  reason  of  this  ?  What  is  the  construction  and  principle  of  Davy's 
safety-lamp  ?  On  what  method  did  Rumford  proceed  to  determine  the 
conducting  power  of  clothing?  What  was  the  effect  of  compression? 
How  are  these  results  connected  with  the  non-conducting  power  of  air  ? 


CONDUCTION    OF    LIQUIDS.  50 

l>e  more  distinctly  seen,  not  so  much  by  their  own  badly- 
conducting  power,  as  by  calling  into  action  the  non-con- 
ducting quality  of  atmospheric  air. 


LECTURE  XIV. 

CONDUCTION. — Conduction  of  Liquids. —  Transference  of 
Heat  by  Circulation. — Conduction  of  Gases. — Conduct  - 
ing  Power  of  Clothing. 

THE  conducting  power  of  most  liquids,  such  Fig.  40. 
as  water,  is  very  low;  a  thin  stratum  is  sufficient 
almost  entirely  to  cut  off  the  passage  of  heat. 
This  may  be  shown  by  an  apparatus  such  as  Fig. 
46,  consisting  of  a  jar,  a,  nearly  filled  with  water, 
with  an  air  thermometer  included  in  such  a  man- 
ner that  the  bulb,  £,  is  within  a  short  distance  of 
the  surface,  a  depth  of  a  quarter  of  an  inch  or 
less  intervening.  The  tube  of  the  thermometer 
may  be  passed  through  the  lower  mouth  of  the 
jar,  c,  water-tight  by  means  of  a  cork,  and  the  position 
at  which  the  index-liquid  stands  having  been  marked, 
some  ether  is  poured  on  the  surface  of  the  water,  upon 
which  it  readily  floats^  and  then  set  on  fire.  A  very  volu- 
minous flame  is  the  result,  and  a  great  deal  of  heat  is 
evolved  ;  and,  since  the  bulb  of  the  thermometer  is  appa- 
rently separated  from  the  burning  ether  by  a  thin  film  of 
water  only,  if  the  heat  traversed  that  film  the  thermome- 
ter should  rapidly  move  ;  but  the  experiment  proves  it 
does  not;  and  we  therefore  conclude  that  water  is  a 
very  bad  conductor  of  caloric. 

While  this  conclusion  is  true,  a  little  consideration  will 
show  that  this  experiment  presents  the  facts  in  a  very  de- 
ceptive way ;  and  though,  from  its  imposing  character,  it 
is  generally  relied  on  as  a  complete  proof,  yet  were  wa- 
ter a  much  better  conductor  than  what  it  actually  is,  the 
same  results  would  be  obtained.  All  flames,  as  we  shall 
hereafter  see,  are  hollow ;  they  are  merely  incandescent 
on  the  surface.  A  great  distance,  in  reality,  intervenes  be- 
How  does  the  conducting  power  of  liquids  compare  with  that  of  solids  ? 
How  may  water  be  proved  to  be  a  bad  conductor  ?  What  deceptive  cir- 
cumstances arc  there  in  this  experiment  ? 


60 


CURRENT    ACTION    IN    WATER. 


tween  tHe  thermometer  bulb  and  the  points  of  high  tem- 
perature, and  in  addition,  the  ether  is  rapidly  evaporating 
away  to  feed  the  flame,  and  all  evaporations  are  cooling 
processes. 

To  a  certain  extent,  all  liquids  conduct  heat :  thus,  mer- 
cury is  a  very  good  conductor ;  but  in  those  liquids  of 
which  water  is  the  type  the  dissemination  of  heat  is  chief- 
ly determined  by  the  mobility  of  their  particles,  a  process 
which  passes  under  the  name  of  convection  or  circulation. 
Fig.  47.  The  apparatus,  Fig.  47,  illustrates  the  na- 

ture of  this  process ;  it  consists  of  a  wide 
tube  into  which  water  may  be  poured  ;  the 
lower  portion,  as  high  as  a,  being  colored 
blue  by  the  addition  of  some  coloring  sub- 
stance, the  intermediate  portion,  from  a  to  b, 
being  colorless,  and  the  upper  portion,  from 
b  to  c.  being  tinged  yellow.  Now,  by  the 
application  of  a  red-hot  iron  ring,  <7,  of  such 
a  diameter  that  it  can  surround  the  jar,  a 
space  of  an  inch  or  more  intervening  all 
round,  the  upper,  yellow  portion  may  be 
made  even  to  boil  :  it  shows  no  disposition 
to  intermix  with  the  portions  beneath.  But  if  the  red- 
hot  ring  is  lowered  down  so  as  to  surround  the  blue  por- 
tion, as  it  becomes  warm  it  will  be  found  to  ascend,  first 
through  the  colorless  stratum,  and  finally  through  that 
tinged  yellow,  on  the  top.  When  the  lower  portion  of  a 
liquid  is  warmed,  currents  are  established,  which,  rising 
through  the  strata  above,  bring  about  a  rapid  dissemina- 
tion of  the  heat. 

This  may  also  be  shown  by  taking  a  jar,  Fig. 
48,  <z,  and  filling  it  with  water,  rendered  a 
little  more  dense  by  some  sulphate  of  soda,  so 
as  to  bring  its  specific  gravity  near  that  of  some 
pieces  of  amber  thrown  into  it.  If  a  lamp  now 
be  applied  to  the  bottom  of  the  jar,  currents 
are  established  in  the  water,  rising  up  the  cen- 
ter and  descending  down  the  sides  of  the  li- 
quid ;  and  in  this  manner,  new  portions  con- 
stantly presenting  themselves  on  the  surface 

Do  liquids  conduct  heat  at  all  ?  What  are  the  relations  of  mercury  iq 
this  respect  ?  By  what  process  does  the  dissemination  of  heat  in  a  liquid 
take  place  ?  Describe  the  experiment  represented  in  Fig.  47.  Describa 
that  represented  by  Fig.  48. 


Fig.  48. 


PROPAGATION    OF    HEAT    IN    LIQUIDS.  61 

exposed  to  the  flame,  the  whole  mass  becomes  uniformly 
hot. 

The  cause  of  this  movement  is  due  to  the  fact  that 
when  water  is  heated  it  expands.  Those  portions,  there- 
fore, which  rest  on  the  bottom  of  the  vessel,  and  to  which 
the  heat  is  applied,  as  soon  as  they  become  warm,  dilate, 
and,  being  lighter  than  before,  rise  to  the  top  of  the  liquid, 
while  colder,  and  therefore  heavier  ones,  occupy  their 
place. 

If  we  take  a  jar  of  water,  Fig.  49,  and  hav-      Fig.  49 
ing  introduced  through  apertures  near  the  top 
and  the  bottom  the  thermometers  a  b,  and  into 
a  brass  trough,  c,  which  surrounds  the  middle 
of  the  jar  water-tight,  pour  boiling  water,  after 
a  little  time  has  elapsed  we  shall  find  that  the 
upper  thermometer  has  risen,  but  the  lower 
one  remains  perfectly  stationary.     The  cause 
is,  that  through  all  those  portions  which  are  above  the  place 
at  which  the  heat  is  applied,  that  is,  the  middle  of  the  ves- 
sel, currents  are  made  to  circulate,  but  in  all  those  be- 
neath no  currents  are  established. 

When,  therefore,  heat  is  applied  to  the  surface  of  wa- 
ter, it  is  not  propagated  downward ;  when  it  is  applied  to 
the  middle  of  a  vessel  containing  that  liquid,  all  the  por- 
tions above  become  hot,  but  all  those  below  remain  cold ; 
and  when  it  is  applied  to  the  bottom  of  the  vessel,  the 
whole  mass  soon  becomes  uniformly  warm. 

In  the  vegetable  world,  advantage  is  taken  of  the  non- 
conducting power  of  water  in  a  very  beautiful  way.  Soon 
after  sunset,  the  leaves  and  other  delicate  parts  of  plants 
become  covered  with  little  drops  of  dew,  which  invest 
them  on  all  sides.  Under  these  circumstances  the  pro- 
cess of  convection,  or  the  establishment  of  currents,  is  en- 
tirely cut  off,  for  each  of  the  drops  is  isolated,  or  has  no 
communication  with  those  around.  The  cold  air  does  not 
so  suddenly  affect  these  delicate  organs  as  it  would  do 
were  not  this  thin  non-conducting  film  spread  over  them ; 
their  action  is,  therefore,  less  liable  to  be  deranged. 

Recent  accurate  experiments  show  that  all  liquids  con- 

What  is  the  true  canse  of  these  circulatory  movements  ?  How  can  it  be 
proved  that  the  warm  water  floats  on  the  surface  of  that  which  is  cold  ? 
What  is  the  effect  of  applying  heat  to  the  top,  to  the  middle,  and  to  the 
bottom  of  a  vessel  containing  water  ?  What  advantage  is  taken  in  the 
vegetable  world  of  the  non-conducting  power  of  water? 


62         PROPAGATION  OF  HEAT  IN  GASES. 

duct  to  a  certain  extent,  though  in  many  instances  to  a  far 
less  extent  than  what  we  see  in  the  case  of  solid  bodies 
Among  different  liquids,  difference  in  conducting  power 
has  also  been  discovered. 

If  the  conducting  power  of  liquids  is  small,  that  of  gas- 
eous bodies  is  still  les&  perceptible.  In  these,  as  in  li- 
quids, the  mobility  of  the  particles  is  so  great  that  heat  is 
Fig.  50.  readily  diffused  through  them.  Thus,  if  we 
take  a  jar,  Fig.  50,  containing  oxygen  gas, 
and  place  a  piece  of  burning  sulphur  in  it  on 
a  stand,  a,  the  vapor  which  rises  from  the  sul- 
phur moves  in  a  current  to  the  top  of  the  jar, 
and  then  descends  in  beautiful  wreaths  of 
smoke  down  the  sides,  precisely  representing 
the  circulatory  movements  of  liquids. 

The  ventilation  of  buildings  and  mines,  and 
the  proper  construction  of  furnaces  and  chimneys,  depend 
upon  these  principles. 

By  taking  advantage  of  the  non-conducting  power  of 
air,  rooms  may  be  kept  warm  with  a  small  consumption 
of  fuel,  by  furnishing  them  with  double  windows.  A 
stratum  of  air,  two  or  three  inches  thick,  intervening 
between  the  windows  effectually  cuts  off  the  passage  of 
heat.  It  is  upon  the  same  principle  we  explain  Count 
Rumford's  experiments  in  relation  to  the  conducting 
power  of  clothing ;  he  found  that  when  the  same  fibres 
are  used,  the  apparent  facility  with  which  they  transmit 
heat  depends  on  the  closeness  with  which  they  are  pack- 
ed :  the  non-conducting  power  of  air  is  here  evidently 
called  into  play,  and  the  fibres  act  by  preventing  the 
production  of  currents.  In  the  case  of  sheep,  or  other 
animals,  which,  during  the  winter  season,  are  covered 
with  a  thick  coat  of  wool,  or  fur,  it  is  the  non-conducting 
power  of  the  included  air  which  is  again  brought  into 
operation. 

Do  all  liquids  conduct  heat  ?  Are  there  differences  in  their  conducting 
power?  By  what  process  is  heat  diffused  through  gases?  What  is  the 
use  of  double  windows  ?  What  connection  has  the  non-conducting  power 
of  air  with  Count  Rumford's  experiments  1  In  the  economy  of  animals, 
what  advantage  is  taken  of  these  principles  ? 


NATURE    OF    RADIANT    HEAT.  63 


LECTURE  XV. 

RADIATION. — Preliminary  Ideas  on  Radiant  Heat. — Anal- 
ogies with  Light. — Effect  of  Surfaces. — ^Relations  be- 
tween Radiation  and  Reflection. —  The  Florentine  Ex- 
periment. —  The  Cold-ray  Experiment.  —  Opacity  of 
Glass  to  Heat.-^—Its  increasing  Transparency  as  the 
Temperature  rises. — Properties  of  Rock  Salt. 

BUT,  though  gases  are  bad  conductors  of  heat,  they 
freely  allow  of  its  transmission  by  general  radiation.  A 
person  who  stands  at  one  side  of  a  fire  receives  the  heat 
of  it,  although  no  currents  of  warm  air  can  reach  him.  In 
a  vacuum,  a  piece  of  red-hot  metal  rapidly  cools. 

The  heat  which,  under  these  circumstances,  escapes 
from  bodies  is  entirely  invisible  to  the  eye ;  it  moves  in 
straight  lines,  exhibiting  many  of  the  phenomena  of  the 
rays  of  light.  Thus,  if  we  interpose  between  a  fire  and  a 
thermometer  an  opaque  screen,  the  moment  the  rays  of 
light  are  stopped  the  heat  is  simultaneously  intercepted. 

The  rays  of  heat,  like  the  rays  of  light,  are  capable  of 
being  reflected  "by  polished  metallic  surfaces.  If  a  piece 
of  planished  tin  be  held  before  a  fire  in  such  a  position  as 
to  reflect  the  light  of  it  upon  the  face,  the  heat,  also,  is 
similarly  reflected,  and  gives  rise  to  a  sensation  of  warmth. 

The  analogy  between  light  and  heat  is  farther  observed 
when  rays  of  the  latter  fall  upon  bodies  of  a  different 
physical  constitution  from  the  metals.  As  glass  is  trans- 
parent to  light,  there  are  many  bodies  transparent  to  rays 
of  heat,  though,  as  we  are  presently  to  find,  these  bodies 
are  not  the  same  in  both  instances.  And  as  there  are 
substances,  like  lamp-black,  which  will  absorb  all  the  light 
which  impinges  on  them,  there  are  many  which  perfectly 
absorb  heat:  reflection,  transmission,  and  absorption  are 
therefore  common  to  both  these  agents. 

If  we  take  two  metallic  vessels  of  the  same  size  and 
shape,  and  having  blackened  one  of  them  all  over  with 

Do  gases  transmit  radiant  heat  ?  How  may  it  be  proved  that  radiant 
heat  moves  in  straight  lines  ?  Is  it  capable  of  reflection  1  Are  there  any 
substances  transparent  to  radiant  heat  ?  Are  these  the  same  bodies  Unit 
are  transparent  to  light  ? 


64 


VARIATION    OF    SURFACE    RADIATION. 


Fig.  51. 


the  smoke  of  a  candle,  fill  them  both  with  hot  water,  and 
notice  their  rate  of  cooling,  it  will  be  seen  that  the  black- 
ened one  cools  faster ;  the  same  thing  may  be  observed,  if, 
instead  of  blackening  the  vessel,  it  is  covered  with  layers  of 
varnish.  These  results  may  be  proved  by  the  aid  of  Les- 
lie's canister,  which  consists  of  a  cubical  brass  vessel,  a, 

Fig.  51,  set  upon  a  verti- 
cal stem,  upon  which  it 
can  rotate  ;  at  a  little  dis- 
tance is  placed  the  black- 
ened bulb  of  a  differential 
thermometer,  d;  a  mirror, 
Jkf,  receives  the  rays  of 
the  canister  and  reflects 
them  on  the  thermometer. 
One  of  the  vertical  sides  of  the  cube  is  left  with  a  clear 
metallic  surface,  a  second  washed  over  with  one  coat  of 
varnish,  the  third  with  two,  and  the  fourth  with  three 
coats ;  if  these  sides  be  presented  in  succession  to  the 
thermometer,  they  will  be  found  to  radiate  heat  with 
very  different  degrees  of  speed,  more  heat  escaping  from 
them  as  the  number  of  coats  is  increased.  In  the  exper- 
iments of  Melloni,  it  was  found  that  the  maximum  was 
not  attained  until  sixteen  coats  were  applied. 

These  results  can  only  be  explained  on  the  principle 
that  radiation  does  not  take  place  from  the  surface  of 
bodies  merely,  but  from  a  certain  depth  in  their  interior. 
A  highly-polished  metal  is  a  bad  radiator,  but  on  rough- 
ening the  surface,  its  quality  is  improved.  As  a  general 
rule,  good  radiators  are  bad  reflectors,  and  good  reflectors 
are  bad  radiators. 

When  rays  of  light,  diverging  from  the  focus  of  a  con- 
cave parabolic  mirror,  impinge  on  the  surface,  they  are  re- 
flected in  parallel  lines  ;  when  parallel  rays  fall  on  such 
a  surface,  they  are  reflected  to  its  focus.  Thus,  if  from 
the  point  # ,  Fig.  52,  the  focus  of  a  parabolic  concave,  c 
f,  rays  diverge,  they  will  be  reflected  in,  parallel  lines,  c  g, 

Of  two  surfaces,  one  polished  and  the  other  blackened,  which  radiates 
heat  best  ?  When  successive  layers  of  varnish  are  put  on  a  surface,  what 
is  their  effect  ?  When  is  the  maximum  reached  ?  What  is  the  explana- 
tion of  these  results  ?  What  is  the  general  connection  between  radiation 
and  reflection  ?  When  rays  diverge  from  the  focus  of  a  concave  mirror, 
what  is  their  path  after  reflection  ?  When  parallel  rays  fall  on  a  concave 
mirror,  what  is  their  path  after  reflection  ? 


EXPERIMENT    WITH  .  CONJUGATE      MIRRORS. 


65 


d  li,  e  i^fk,  and  if  at  these  points  they  be  intercepted  by 
the  mirror,  g  k,  they  will  be  reflected  to  its  focus,  b. 

Now,  as  the  laws  of  reflection  of  radiant  heat  are  the 
same  as  the  laws  of  the  reflection  of  light,  it  is  plain  that 
if  we  place  any  incandescent  body,  such  as  a  red-hot 
cannon-ball,  in  the  focus,  a,  the  heat  which  radiates  from 
it  will  finally  be  found  at  the  other  focus,  b. 

Fig.  52. 


*  This  is  beautifully  illustrated  by  an  experiment  known 
under  the  name  of  the  experiment  with  conjugate  mir- 
rors. In  the  focus,  a,  Fig.  52,  of  a  parabolic  mirror,  cft 
place  a  red-hot  cannon-ball,  and  in  the  focus,  b,  of  a 
second  mirror,  g  k,  set  opposite,  but  twenty  or  thirty 
feet  off,  place  a  piece  of  phosphorus,  a  screen  intervening 
between.  As  soon  as  the  arrangements  are  completed, 
remove  the  screen,  and  in  a  moment  the  phosphorus  takes 
fire.  That  this  effect  is  due  to  the  reflecting  action  of  the 
mirrors,  as  has  been  described,  may  be  proved  by  re- 
moving the  mirror,  c  f,  when  it  will  be  found  that  the 
phosphorus  can  not  be  lighted,  even  though  the  ball  be 
brought  within  a  very  short  distance  of  it. 

This  striking  experiment  proves,  first,  that  the  rays  of 
heat  move  in  straight  lines,  like  those  of  light ;  and,  sec- 
ond, that  in  the  same  manner  they  are  subject  to  the  ordi- 
nary laws  of  reflection. 

A  variation  of  the  foregoing  experiment  may  be  made 

"When  a  hot  ball  is  placed  in  the  focus  of  one  of  the  mirrors,  to  what 
point  does  its  heat  converge  ?  Describe  the  Florentine  experiment  rep- 
resented in  Fig.  52.  What  two  facts  does  this  experiment  prove  ? 

F2 


66  OPACITY    OF    GLASS    TO    HEAT. 

by  using  a  snowball  instead  of  the  cannon-shot,  in  which 
case  a  thermometer  placed  in  the  focus  of  the  opposite 
mirror  will  exhibit  a  reduction  of  temperature.  From 
this  it  was  at  one  time  supposed  that  there  existed  rays 
of  cold  precisely  analagous  to  rays  of  heat,  and  that  they 
observed  the  same  law  as  respects  the  rectilinear  nature 
of  their  movement,  and  were  also  subject  to  the  law  of  re- 
flection ;  but,  as  we  shall  see  when  we  come  to  speak  of 
the  Theory  of  the  Exchanges  of  Heat,  a  simple  explana- 
tion of  the  whole  result  can  be  given,  without  implying 
the  existence  of  a  principle  of  cold  analogous  to  the  prin- 
ciple of  heat. 

L  et  it  be  now  supposed  that  in  the  focus  of  the  mirror, 
g  k,  Fig.  52,  the  bulb  of  a  delicate  thermometer  is  placed, 
and  in  the  focus  of  the  other  mirror,  cf,  a  metalline  mass, 
a,  the  temperature  of  which  we  can  vary  at  pleasure. 
Between  the  mirrors  let  there  be  interposed  a  screen  of 
transparent  plate  glass  ;  and  let  us  farther  suppose  that 
the  temperature  of  a  is  212°,  or  considerably  below  the 
point  at  which  it  is  visibly  red  hot.  Under  these  circum- 
stances the  thermometer  exhibits  no  rise  of  temperature 
BO  long  as  the  glass  intervenes,  but  the  moment  it  is  re- 
moved the  heat  passes. 

A  piece  of  transparent  glass  is,  therefore,  opaque  to 
the  rays  of  heat  which  come  from  a  non-luminous  source. 

Let  us  now  suppose  that  the  temperature  of  the  metal- 
line mass,  #,  continually  rises.  When  it  has  reached  a 
red  heat,  a  certain  proportion  of  the  rays  emitted  by  it 
begins  to  pass  through  the  glass,  as  is  shown  by  their 
effect  upon  the  thermometer.  When  the  mass  is  visibly 
red  hot  in  the  daylight  the  rays  go  through  the  glass  more 
readily,  and  when  it  has  become  white  hot,  or  has  reached 
the  highest  temperature  we  can  give  it,  the  glass  trans- 
mits the  rays  with  facility. 

These  facts  are  of  the  utmost  importance.  They  show 
that  bodies  transparent  to  light  are  not  necessarily  trans- 
parent to  heat,  and,  therefore,  that  light  and  heat  are 
separate  and  independent  agents.  They  farther  show, 
that,  as  respects  glass,  its  transparency  for  heat  differs 

When  a  snowball  is  used  instead  of  a  hot  shot,  what  is  the  result  ? 
What  is  the  relation  of  glass  to  radiant  heat  of  low  intensity  ?  What 
changes  take  place  in  the  transmissive  power  of  the  glass  as  the  tem- 
perature rises  ?  How  are  these  facts  connected  with  the  physical  inde- 
pendence of  light  and  heat  ? 


RADIANT    HEAT    OF    DIFFERENT    COLORS.  67 

with  the  temperature  of  the  source  from  which  the  rays 
come. 

There  is  a  certain  well-known  substance,  rock  salt,  with 
which,  if  we  could  obtain  plates  large  enough  to  inter- 
vene completely  between  the  two  mirrors,  a  different 
series  of  results  would  be  exhibited.  Whatever  might 
be  the  temperature  of  the  source,  whether  low  or  high, 
the  rays  would  pass  it  with  equal  freedom.  The  warmth 
of  the  hand  and  the  rays  from  melting  iron  would  go 
through  it  alike.  This  .substance,  therefore,  is  permeable 
to  all  kinds  of  heat,  as  glass  is  permeable  to  all  kinds  of 
light.  It  constitutes  the  true  glass  for  heat. 

The  great  conclusion  which  we  draw  from  the  experi- 
ments just  described  is,  that  there  are  different  varieties  of 
radiant  heat.  Some  of  them  can  pass  through  glass,  and 
some  can  not.  Hereafter  we  shall  see  that  the  intrinsic 
differences  in  radiant  heat  are  due  to  the  same  cause 
which  gives  different  colors  to  light. 


LECTURE  XVI. 

THEORY  OF  THE  EXCHANGES  OF  HEAT. — Physical  Inde 
pendence  of  Light  and  Heat. —  Theory  of  Exchanges. — 
Explanation   of  the  Cold  Ray  Experiment. —  Wells' s 
Theory  of  the  Dew. —  Cold  on  Mountain  Tops. — Con- 
duction a  Form  of  Hadiation. —  Temperature  of  the  Sun. 

THE  earlier  writers  on  chemistry  supposed  that  if  light 
and  heat  are  not  the  same  principle,  they  are  mutually 
convertible;  that  when  the  rays  of  light  fall  on  any  ob- 
ject and  warm  it,  they  do  so  because  they  become  ex 
tinguished  and  changed  into  heat. 

But  there  are  many  facts  which  militate  against  this 
doctrine.  A  vessel  containing  hot  water  radiates  heat, 
and  that  heat  is  totally  invisible  in  a  dark  room,  nor  can 
it  be  made  to  assume  the  luminous  condition,  even  though 
concentrated  by  large  concave  mirrors. 

What  are  the  properties  of  rock  salt  ?  Why  is  it  the  glass  of  heat? 
What  general  conclusion  is  drawn  from  the  foregoing  facts  ?  What  are 
the  varieties  of  radiant  heat  due  to  ?  What  relation  was  formerly  sup- 
posed to  exist  between  light  and  heat  ?  Can  rays  of  heat  exist  without 
being  visible  T 


68         THEORY  OF  EXCHANGES  OF  HEAT. 

Experiments  have  been  made  to  determine  whether  in 
the  moonbeams  there  are  any  calorific  rays.  The  most 
delicate  thermometers,  aided  by  concave  mirrors,  have 
hitherto  failed  in  detecting  the  minutest  trace.  In  this  in- 
. stance,  therefore,  we  have  light  existing  without  heat;  in 
the  former,  heat  existing  without  light. 

In  addition,  as  we  have  already  shown,  the  relation  of 
transparency  for  these  two  agents  is  not  the  same.  A 
piece  of  smoky  quartz,  or  dark-colored  mica,  of  such  a 
degree  of  opacity  as  scarcely  to  admit  a  ray  of  light  to 
pass,  is  freely  traversed  by  radiant  heat. 

The  theory  of  the  exchanges  of  heat,  comprehending 
an  explanation  of  a  great  number  of  the  phenomena  we 
ordinarily  witness,  depends  upon  the  following  principles  : 
It  assumes,  1st,  that  all  bodies,  no  matter  what  their  tem- 
perature may  be,  are  constantly  radiating  heat  at  all  times; 
2d.  That  the  rate  of  radiation  depends  on  the  tempera- 
ture, increasing  as  the  temperature  rises,  and  diminishing 
as  it  declines. 

Thus  the  various  objects  around  us  are  constantly  emit- 
ting caloric :  the  warm  bodies  to  the  cold,  and  the  cold 
ones  to  the  warm.  A  mass  of  snow  and  a  red-hot  cannon- 
ball  respectively  give  off  heat,  the  ball  emitting  it  in  great 
quantities,  and  the  snow  in  less.  And  even  when  adja- 
cent bodies  have  reached  the  same  thermometric  point, 
they  still  continue  to  exchange  heat  with  one  another. 

Upon  these  principles,  we  can  readily  account  for  the 
fact  that  bodies  of  different  temperatures  at  first,  finally 
come  to  an  equilibrium.  If  an  ignited  cannon-shot  be 
placed  in  the  middle  of  a  large  room,  it  radiates  its  heat 
to  the  roof,  the  walls,  the  floor,  .and  the  various  objects 
around  :  they  also  radiate  back  again  upon  it ;  but,  from  its 
elevated  temperature,  it  emits  its  heat  faster  than  they,  and 
therefore  gives  out  more  than  it  receives.  Its  tempera- 
ture constantly  descends,  and  continues  to  do  so  until  it 
receives  just  as  much  as  it  gives,  which  takes  place  when 
it  has  reached  the  same  degree  as  the  objects  around; 
for,  other  things  being  equal,  bodies  at  the  same  temper- 
ature radiate  with  equal  speed. 

Call  light  exist  unaccompanied  by  heat  1  What  other  evidence  have 
we  of  the  physical  independence  of  these  agents  ?  On  what  does  the 
theory  of  the  exchanges  of  heat  depend  1  Do  bodies  at  the  same  tem- 
perature still  radiate  ?  Describe  the  process  of  cooling  of  an  incandescent 


THE    COLD-RAY    EXPERIMENT.  69 

The  process  must,  however,  stop  as  soon  as  that  equal- 
ity of  temperature  is  attained  ;  for,  if  we  suppose  the  shot 
to  cool  below  that  point,  it  would  evidently  begin  to  re- 
ceive more  heat  from  the  objects  around  than  it  gave  forth, 
and  the  excess  accumulating  in  it,  its  temperature  would 
at  once  rise. 

When  an  equilibrium  is  obtained  the  process  of  radia- 
tion still  continues,,  but  the  exchanges  are  equal.  Two 
lighted  candles  placed  together  do  not  extinguish  each 
other,  or  cease  to  exchange  light  with  each  other,  nor  do 
two  bodies  equally  warm  cease,  for  that  reason,  to  exchange 
heat.  In  a  room,  therefore,  in  which  every  thing  has  the 
same  temperature,  rays  are  eternally  exchanging,  but  each 
object  maintains  its  own  temperature,  because  it  receives 
as  much  as  it  gives. 

If  a  red-hot  ball  and  a  thermometer  bulb  are  placed 
near  one  another,  the  bulb  receives  more  heat  from  the 
ball  than  it  gives  to  it,  and  its  temperature  therefore  rises ; 
but,  if  a  thermometer  bulb  and  a  snowball  are  placed  in 
presence  of  one  another,  the  bulb,  being  the  hotter  body, 
gives  more  than  it  receives,  and  its  temperature  therefore 
descends.  This  is  the  explanation  of  the  experiment  with 
the  conjugate  mirrors.  That  experiment,  as  was  observ- 
ed, affords  no  proof  that  there  are  rays  of  cold  :  the  ef- 
fect is  due  to  the  fact  that  a  mutual  exchange  is  going 
forward  between  the  two  bodies,  and  the  temperature  of 
the  hotter  descends.  The  mirrors,  of  course,  take  no 
part  in  this  phenomenon ;  their  office  is  merely  to  direct 
the  path  of  the  rays,  as  has  been  explained. 

On  the  principles  of  the  radiation  of  heat  is  founded 
Wells's  theory  of  the  dew.  After  the  sun  goes  down  of  an 
evening,  drops  of  water  condense  on  the  leaves,  grass, 
stones,  and  other  objects  exposed  to  the  air.  It  was  once 
a  question  whether  this  dew  descended  in  the  form  of  a 
light  shower,  or  ascended  from  the  ground.  There  are 
also  certain  circumstances  apparently  very  mysterious  at- 
tending its  formation :  the  dew  rarely  falls  on  a  cloudy 
night ;  it  also  apparently  possesses  a  selecting  power,  de- 

When  does  the  descent  of  temperature  cease  ?  When  an  equilibrium 
is  obtained,  what  is  the  rate  of  the  exchanges  ?  Describe  the  action  in 
the  case  of  a  red-hot  ball  and  a  thermometer  bulb.  Describe  the  action  of 
a  snowball  and  a  thermometer  bulb.  How  is  this  connected  with  the  ex- 
periment with  conjugate  mirrors  ?  Under  what  circumstances  does  dew 


70  THEORY    OF    THE    DEW. 

positing  itself  on  some  bodies  in  preference  to  others. 
The  theory  of  Dr.  Wells  furnishes  a  beautiful  explanation 
of  these  curious  facts.  During  the  day,  the  various  bod- 
ies on  the  surface  of  the  earth,  receiving  the  rays  of  the 
sun,  become  warm ;  but  at  nightfall,  when  the  sky  is  un- 
clouded, they  begin  to  cool ;  for,  the  process  of  radiation 
continuing  without  any  source  of  supply,  their  tempera- 
ture must  descend.  White  the  sun  shone,  they  received 
as  much  heat  from  him  as  they  gave  forth  to  the  sky,  but 
when  he  sets,  the  supply  is  cut  off,  and  they  therefore 
cool ;  and  as  there  is  always  moisture  in  the  air,  their 
temperature  descending,  by-and-by  the  dew  point  is  reach- 
ed ;  they  become  cold  enough  to  condense  water  from  the 
surrounding  air,  and  this  is  the  dew.  And  as  different 
bodies,  according  to  the  roughness  or  physical  condition 
of  their  surfaces,  radiate  with  different  degrees  of  speed, 
as  Leslie's  canister  proves,  some  of  the  objects  exposed 
to  the  sky  cool  rapidly,  and  are  covered  with  dew ;  but 
with  others  the  dew  point  is  never  reached :  hence  the 
apparent  selecting  power.  When  there  is  a  canopy  of 
clouds  over  the  sky,  dew  can  not  form,  for  the  cloud  ra- 
diates to  the  earth  as  much  as  the  earth  radiates  to  it :  the 
exchanges  are  equal,  and  the  equilibrium  is  maintained  ; 
but  if  the  cloud  disappears,  the  heat  of  the  surface  of  the 
ground  escapes  away  into  the  regions  of  space,  and  is 
lost ;  hence  cloudy  nights  are  warm,  and  a  clear  is  often 
a  frosty  night. 

For  similar  reasons,  mountain  tops  are  always  colder 
than  valleys.  In  a  valley,  the  radiation  is  obstructed  by 
the  sides  of  the  adjacent  hills,  but  on  the  top  of*a  mount- 
ain the  free  exposure  to  the  sky  permits  of  unchecked 
radiation. 

It  has  already  been  observed,  that  conduction  is  only  a 
form  of  radiation.  In  its  ordinary  acceptation,  the  term 
conduction  implies  passage  from  particle  to  particle,  by 
reason  of  their  being  in  contact ;  but  we  have  proved  that 
the  constitution  of  matter  involves  the  existence  of  inter- 
stices, and  that  heat  can  only  pass  from  among  these  by 
radiating  across  the  interstices  ;  hence  the  term  interstitial 
radiation.  ~- 

What  is'  the  theory  of  Wells  ?  How  does  this  explain  the  selecting 
power  of  bodies  ?  How  does  it  explain  the  action  of  clouds  ?  Why  is  it 
colder  on  mountains  than  in  valleys  ?  What  is  meant  hy  interstitial  ra- 
diation ? 


NATURE    OF   LIGHT.  71 

An  interesting  conclusion  may  be  drawn  from  the  con- 
ditions of  the  passage  of  radiant  heat  through  glass.  We 
have  seen  it  is  necessary  that  the  heat  should  come  from 
a  source  of  very  high  temperature  to  pass  this  medium 
with  facility.  Now  the  heat  of  the  sun  passes  with  the 
greatest  freedom,  as  is  well  known  when  we  stand  before 
a  window  through  which  the  sun  shines.  In  the  focus  of 
a  convex  lens  of  glass  exposed  in  the  sun's  rays,  bodies 
may  be  readily  set  on  fire.  We  infer,  therefore,  that  the 
temperature  of  the  sun  is  very  high ;  a  result  which  is 
corroborated  by  proofs  drawn  from  other  sciences. 


LECTURE  XVII. 

NATURE  OF  LIGHT. —  Vibratory  Movement  the  Cause  oj 
Light. — Evolution  of  Light  by  Rise  of  Temperature. — 
Case  of  Gases. — Nature  of  Flame. — Artificial  Lights 
of  various  Colors. — General  Properties  of  Light. —  The 
Prism.  —  Decomposition  of  Light  by  it.  —  Nature  of 
White  Lights — Newton's  Theory  of  different  Refrangi- 
bility. 

THE  phenomena  of  radiant  heat  lead  us  by  impercep- 
tible steps  to  the  phenomena  of  light.  In  treating  of  the 
former,  we  have  in  many  cases  drawn  illustrations  from 
the  latter ;  and,  indeed,  there  are  facts  in  relation  to  ca-  • 
loric  which  it  is  absolutely  impossible  to  understand  until 
we  comprehend  the  analogous  facts  in  light.  Such,  for 
instance,  is  the  theory  which  I  have  designated  "  The 
Theory  of  Ideal  Coloration,"  and  which  by  the  most  em- 
inent writers  is  regarded  as  involving  the  fundamental 
facts  of  the  science  of  radiant  heat. 

Light  is  the  result  of  an  undulatory  or  wave-like  mo- 
tion, propagated  through  the  ethereal  medium,  which  per- 
vades all  space.  These  waves,  impinging  on  the  retina, 
an  expansion  of  the  optic  nerve,  situated  on  the  posterior 
inner  surface  of  the  eye,  produce  in  its  delicate  substance 
a  specific  chemical  change.  There  is  no  difficulty  in  ad- 
mitting that  from  these  changes  impressed  upon  that  sen- 

What  conclusion  may  be  drawn  as  respects  the  temperature  of  the  sun, 
from  the  phenomena  of  radiant  heat  ?  What  is  the  cause  of  light  ?  How 
is  the  influence  of  light  on  the  retina  transmitted  to  the  brain  ? 


72  TRANSMISSION    OP    VIBRATIONS. 

sitive  surface,  a  vibratory  movement  is  transmitted  along 
the  optic  nerve  to  the  brain ;  for,  as  we  shall  see  when  we 
reach  the  description  of  a  simple  voltaic  circuit,  the  oxy- 
dation  of  a  piece  of  zinc  may  raise  the  temperature  of  a 
platina  thread  to  a  red  heat  hundreds  of  miles  off,  the 
movement  being  transmitted  through  a  solid  copper  wire. 
How  much  more,  then,  might  we  expect  to  find  similar 
movements  communicated  through  a  delicate  nervous 
column,  specially  organized  for  their  passage  ] 

Nor  is  there  any  difficulty  in  admitting  that  through 
such  a  channel  an  infinity  of  vibrations  may  simultaneously 
pass,  undisturbed  by  each  other.  All  the  varied  objects 
around  us,  whatever  may  be  their  shape  or  whatever  their 
color,  simultaneously  transmit  through  the  optic  nerve 
their  proper  impressions,  which  are  registered  in  the  brain. 
There  are  similar  phenomena  in  the  case  of  sound ;  thus, 
if  we  take  a  musical  snuffbox,  and,  removing  its  case,  hold 
it  in  the  air,  the  sound  is  so  enfeebled  that  it  is  scarcely 
audible  a  few  feet  off;  but  now,  if  the 
instrument  be  placed  in  the  position  d, 
Fig.  53,  resting  on  a.  block  of  wood, 
e,  which  is  brought  fairly  in  contact  at 
its  lower  end  with  the  table,  a  b,  the 
table  begins  to  resound,  and  the  musi- 
cal notes  are  all  loudly  and  distinctly 
heard.  But  these  vibrations,  into  which 
the  table  is  thrown,  have  all  passed 
through  the  mass  of  wood,  c  ;  if  wre  touch  it,  it  trembles 
beneath  the  finger.  Arid  now,  no  matter  how  shapeless 
that  intervening  mass  may  be,  nor  how  intricate  the  notes 
which  the  instrument  is  executing,  there  is  no  confusion 
nor  intermingling  ;  the  mass  of  wood  and  the  table  on 
which  it  rests  vibrate  in  unison  with  the  musical  mech- 
anism. 

When  the  temperature  of  solid  substances  is  raised  to 
1000°  Fahrenheit,  they  begin  to  be  luminous  in  the  day- 
light, or,  as  it  is  termed,  are  visibly  red  hot.  It  requires 
a  far  higher  temperature  to  render  a  gas  incandescent. 

Are  there  "any  analogous  phenomena  illustrating  the  transmission  of  ef- 
fects through  great  distances  ?  Can  such  vibrations  pass  together  through 
solid  bodies  without  disturbing  one  another  ?  Give  an  illustration  from  the 
phenomena  of  sound.  At  what  temperature  are  solids  luminous  ?  Is  a 
gas  or  a  solid  more  easily  made  incandescent  ? 


ARTIFICIAL    LIGHT.  73 

This  may  be  shown  by  holding  a  piece  of  thin  platina  wire 
in  the  current  of  hot  air  which  rises  from  the  apex  of  the 
flame  of  a  lamp;  the  air  is  not  visibly  ignited,  but  the 
platina  wire  instantly  becomes  red  hot,  showing  the  great 
difference  in  this  respect  between  this  metal  and  a  gas. 

Different  vapors  and  gases  evolve  different  quantities 
of  light  when  ignited.  The  flame  of  burning  hydrogen  is 
scarcely  visible  in  the  daylight ;  that  of  alcohol  is  but  little 
brighter,  but,  under  the  same  circumstances,  sulphuric 
ether  emits  much  light.  If  we  take  a  glass  of  the  form 
Fig.  54,  consisting  of  a  bulb,  a,  and 
curved  tube,  b,  and  having  filled  the 
bulb  with  ether,  cause  it  to  boil  by 
the  application  of  a  lamp,  c,  the 
ether  may  be  sot  on  fire  as  it  is  forced 
out  of  the  vessel  by  the  pressure  of 
its  vapor.  It  burns  in  a  beautiful 
arch  of  great  brilliancy;  but  if  we 
substitute  alcohol  for  ether,  the  light  becomes  quite  in- 
significant. 

The  light  which  is  emitted  by  lamps  and  candles  is, 
however,  in  reality,  due  to  the  disengagement  of  solid 
matter.  The  constituents  of  the  gas  which" produces  the 
flame  are  carbon  and  hydrogen  chiefly ;  of  these,  the  latter 
is  the  more  combustible,  arid  is  first  burned  ;  for  a  moment, 
therefore,  the  carbon  exists  in  a  solid  form,  in  a  state  of 
extreme  subdivision,  and  at  a  high  temperature,  but  being 
in  contact  with  the  external  air,  it  is  immediately  consumed. 

Artificial  lights  differ  in  color.  If  alcohol  be  mixed 
with  common  salt  and  set  on  fire,  the  flame  is  of  a  yellow 
tint ;  if  with  boracic  acid,  it  is  green ;  if  with  nitrate  of 
strontian,  it  is  red.  It  is  upon  these  principles  that  the 
art  of  pyrotechny  depends. 

From  whatever  source  light  may  come,  it  exhibits  the 
same  physical  properties.  It  moves  in  straight  lines. 
When  it  impinges  on  polished  metallic  surfaces,  it  is  re- 
flected ;  on  dark  surfaces,  it  is  absorbed ;  on  transparent 
surfaces,  as  glass,  it  is  transmitted.  In  the  last  case,  it  is 

In  the  combustion  of  vapors  and  gases,  is  there  any  difference  in  the 
amount  of  light  emitted  1  How  may  this  be  illustrated  ?  To  what  cause 
are  we  to  attribute  the  light  emitted  by  lamps  and  candles  ?  How  may 
artificial  yellow,  green,  and  red  lights  be  made?  In  what  course  does 
light  move  ?  What  is  meant  by  the  reflection,  absorption,  transmission, 
and  refraction  of  light  ? 

Gf 


74 


DECOMPOSITION    OF    LIGHT    BY    A    PRISM. 


Fig.  56. 


frequently  forced  into  a  new  path,  as  we  shall  presently 
see,  and  then  the  phenomenon  takes  the  name  of  refrac- 
tion, because  the  ray  is  broken  from  its  primitive  course. 

There  are  two  different  kinds  of  opacity,  black  and 
white;    charcoal  is  a  black  opaque  substance,  earthen- 
Fig.  55.      ware  is  opaque  white. 

Sir  Isaac  Newton  first  succeeded  in  proving 
the  compound  nature  of  light  by  the  aid  of  a 
very  simple  instrument,  a  glass  prism.     It  con- 
sists of  a  piece  of  glass  having  three  sides, 
Fig.  55,  a  a,  and  is  usually  mounted  on  a  brass 
stand,  b,  with  a  ball  and  socket  joint,  c,  which 
allows  us  to  place  it  in  any  required  position. 
Let  the   shutters    of  a   room   be 
closed,  and  through  an  aperture  in 
one  of  them,  suitably  situated,  let  a 
beam  of  the  sun  enter,  Fig.  56,  a.    It 
j    pursues,  of  course,  a  straight  path, 
following  the  dotted  line,  a  e.     Now 
let  the  prism  interpose  in  the  position 
b  c,  so  as  to  intercept  completely  the 
ray.     This  goes  no  longer  to  e,  but  is 
bent  out  of  its  course,  and  moves  in 
the  direction  d. 

Two  striking  facts  are  now  to  be  remarked  :  first,  the 
ray  a  is  refracted  or  broken  from  its  path  ;  and,  second, 
instead  of  forming  on  the  surface  d,  upon  which  it  falls,  a 
white  spot,  an  elongated  and  beautifully- colored  image 
is  produced.  These  colors  are  seven  in  number  :  red, 
yellow,  orange,  green,  blue,  indigo,  violet.  The  separation 
of  these  colors  from  one  another  is  designated  by  the  term 
Dispersion. 

Newton  has  shown  that  white  light  consists  of  these  vari- 
ous-colored rays  blended  together  ;  and  their  separation  in 
the  case  before  us  is  due  to  the  fact  that  the  prism  refracts 
them  unequally.  On  examining  the  position  of  the  colors, 
in  their  relation  to  the  point  e,  to  which  they  would  all 
have  gone  had  not  the  prism  intervened,  it  is  ascertained 
that  the  red  is  least  disturbed  or  refracted  from  its  origi- 

How  many  kinds  of  opacity  are  there  ?  Describe  the  prism.  State  the 
effect  which  ensues  when  a  ray  passes  through  the  prism.  What  is  meant 
by  refraction  ?  What  by  dispersion  ?  What  is  Newton's  theory  of  the 
constitution  of  light  ? 


THE    SOLAR    SPECTRUM.  75 

nal  path,  and  the  violet  most ;  for  these  reasons,  we  call 
the  red  the  least  refrangible  ray,  the  violet  the  most  refran- 
gible, and  the  yellow  intermediately. 

That  the  mixture  of  these  colored  rays  reproduces 
white  light,  may  be  proved  by  resorting  to  any  optical 
contrivance  which  will  reassemble  them  all  in  one  point; 
that  point  will  be  perfectly  white. 


LECTURE  XVIII.     v.  • 

CONSTITUTION  OP  THE  SOLAR  SPECTRUM. — Order  of  the 
Colors. —  Order  of  Intensity  of  the  Light. — Distribution 
of  Heat. —  The  Chemical  Rays. —  Their  Distribution. — 
Constitution  of  the  Solar  Rays. 

LET  v  r,  Fig.  57,  represent  the  spectrum  Fis- 
which  is  given  by  a  sunbeam  after  its  passage 
through  a  prism,  and  e  the  point  to  which  it 
would  have  gone  had  not  the  prism  intervened; 
the  order  of  the  colors  commencing  with  that 
which  is  least  disturbed  from  its  path,  or  nearest 
to  e,  is  as  follows  : 


Red, 
Orange, 

Yellow, 


Blue, 

Indigo, 

Violet. 


Green, 

These  colors  gradually  blend  into  each  other, 
so  that  their  boundaries  can  not  be  traced  ;  and  instead 
of  a  circular  spot,  which  would  have  resulted  had  they 
gone  forward  to  e,  they  are  dilated  out,  so  as  to  form  an 
elongated  figure  with  parallel  sides;  at  the  two  extremi- 
ties the  light  fades  gradually  away,  so  that  we  can  not  trace 
its  limit  with  precision. 

Besides  this  difference  of  color,  the  light  differs  in  in- 
trinsic brilliancy  in  the  different  spaces.  Thus,  if  we  re- 
ceive the  spectrum  on  a  piece  of  finely-printed  paper,  wo 
can  read  the  letters  in  each  color  at  very  different  dis 
tances.  In  the  yellow  region  the  light  is  most  brilliant, 
and  there  we  can  read  farthest.  From  this  point  the  light 
declines  in  brilliancy  to  the  two  ends  of  the  spectrum,  its 

Which  is  the  least,  and  which  the  most  refrangible  ray  ?  Of  what  doe* 
white  light  consist  ?  What  is  the  order  of  refrangibility  of  colors  ?  What 
is  the  figure  of  the  spectrum  ?  How  may  the  illuminating  power  be  de 
termined  ? 


76  DISTRIBUTION    OF    HEAT    IN    THE    SPECTRUM. 

intensity  in  the  colored  spaces  being  in  the  following  01 
der: 


Yellow, 
Green, 
Orange, 


Blue, 

Indigo, 

Violet. 


Bed, 

Sir  W.  Herschel  discovered,  while  using  large  reflecting 
telescopes,  that  the  calorific  rays  of  the  sun  pass  with  dif- 
ferent degrees  of  facility  through  colored  glasses,  and  was 
led  to  examine  the  temperature  of  the  colored  spaces  of 
the  solar  spectrum,  to  see  whether  the  intensity  of  the  heat 
follows  the  intensity  of  the  light.  It  was  reasonable  to 
suppose  that  the  yellow  space,  being  the  brightest,  would 
P.  5g  be  also  the  hottest.  He  therefore  placed  delicate 
thermometers  in  the  various  colored  spaces,  and 
3  kept  them  in  these  spaces  until  they  had  risen  as 
high  as  the  ray  could  bring  them.  The  thermom- 
eter v,  Fig.  58,  has  risen  the  least,  and  in  suc- 
,  cession,  i,  b,  g,  y,  o,  r  ;  that  which  was  immersed 
,  in  the  red  being  the  highest. 

It  thus  appears  that  the  distribution  of  heat  in 
"  the  colored  spaces  of  the  solar  spectrum  is  not  the 
same  as  the  distribution  of  light  j  that  the  yellow 
ray,  though  it  is  the  most  luminous,  is  far  from 
being  the  hottest,  and  that  the  intensity  of  the  heat  stead- 
ily increases  from  the  violet  to  the  red  extremity. 

But  this  is  not  all :  he  farther  found,  that  if  a  thermom- 
eter be  brought  out  of  the  red  region  in  the  position  x,  be- 
yond the  limits  of  the  spectrum,  and  where  there  is  no 
light  whatever,  it  stands  higher  than  any  of  the  others. 
From  this  a  most  important  conclusion  is  to  be  drawn, 
that  the  light  and  heat  existing  in.  the  sunbeam  are  dis- 
tinct and  independent  agents,  and  that  by  such  processes 
as  we  are  considering  they  may  be  perfectly  separated 
from  each  other. 

It  was  discovered  by  some  of  the  alchemists,  centuries 
ago,  that  the  chloride  of  silver,  a  substance  of  snowy  white- 
ness, turns  black  on  exposure  to  the  light.  More  recent- 
ly, a  great  number  of  such  bodies  have  been  found — bod- 

What  is  the  order  of  illuminating  power  ?  Describe  the  discovery  of 
Sir  W.  Herschel.  Is  the  distribution  of  heat  in  the  spectrum  the  same  as 
the  distribution  of  light?  What  fact  indicates  that  the  light  and  heat  are 
Beparate  and  independent  agents  ?  What  changes  does  chloride  of  silver 
undergo  in  the  sunshine  ? 


RAYS    OF    CHEMICAL    ACTION.  77 

ies  which  change,  with  greater  or  less  rapidity,  under  the 
influence  of  this  agent.  The  iodide  of  silver,  which  forms 
the  basis  of  the  process  known  as  the  Daguerreotype,  is 
such  ;  and  a  mixture  of  chlorine  and  hydrogen  gases  in 
equal  volumes,  though  it  may  be  kept  unchanged  for  a 
great  length  of  time  in  the  dark,  explodes  violently  on  ex- 
posure to  the  sunshine.  In  the  same  manner  changes  take 
place  in  a  great  variety  of  organic  compounds  ;  the  most 
delicate  vegetable  hues  are  soon  bleached,  and,  indeed,  a 
ray  of  light  can  scarcely  fall  on  a  surface  of  any  kind 
without  leaving  traces  of  its  action. 

If  a  piece  of  paper,  spread  over  with  chloride  of  silver, 
be  placed  in  the  solar  spectrum,  it  soon  begins  to  blacken. 
But  it  does  not  blacken  with  equal  promptitude  in  each 
of  the  colored  spaces  ;  the  effect  takes  place  most  rapidly 
among  the  more  refrangible  colors,  and  especially  in  the 
violet  region.  As  in  the  case  of  heat,  the  effect  extends 
far  beyond  the  limit  of  the  spectrum,  and  where  the  eye 
can  not  discover  a  trace  of  light.  We  are  led,  therefore, 
to  conclude  that  there  exists  in  the  sunbeam  an  agent  ca- 
pable of  producing  chemical  effects,  which  exerts  no  action 
on  a  thermometer,  which  can  not  be  perceived  by  the  eye, 
and  which  therefore  is  neither  heat  nor  light. 

By  placing  mixtures  of  chlorine  and  hydrogen  in  small 
vials,  and  immersing  them  in  the  colored  spaces,  we  can 
readily  determine  the  place  of  maximum  action,  and  the 
distribution  of  the  chemical  influence  throughout  the 
spectrum.  In  this,  as  in  the  former  instance,  the  greatest 
effect  is  found  among  the  more  refrangible  colors,  and 
from  that  point  diminishes  toward  each  extremity  of  the 
spectrum. 

As  the  general  result  of  this  examination  of  the  solar 
spectrum,  we  finally  come  to  the  conclusion  that  light,  far 
from  being  a  simple,  is  a  very  complex  agent ;  that  there 
exist  in  the  sunbeam  at  least  three  separate  principles : 
one  which  excites  in  our  bodies  the  sensation  of  warmth ; 
a  second  which,  from  its  influence  on  the  organs  of  vision, 
we  recognize  as  light ;  and  a  third  which  determines  the 

When  a  mixture  of  chlorine  and  hydrogen  is  exposed  to  the  sun,  what  oc- 
curs ?  How  does  light  change  vegetable  colors  ?  Which  ray  darkens  the 
chloride  of  silver  most  1  What  proof  have  we  that  another  agent  exists  in 
the  sun's  rays  besides  light  and  heat  ?  What  ray  affects  the  mixture  of 
chlorine  and  hydrogen  most  powerfully  ?  What  is  the  general  result  as 
respects  the  constitution  of  the  sunbeam  ? 

G2 


78  PHOSPHOROGENIC    RAYS. 

production  of  chemical  changes.  Future  discovery  may 
show  that  these  are  modifications  of  one  common  princi- 
ple, but  in  the  present  position  of  science  we  are  obliged 
to  regard  them  as  essentially  distinct. 

Besides  these  three  principles,  there  are  several  facts 
which  point  out  the  existence  of  a  fourth.  When  oyster- 
shells  have  been  calcined  with  sulphur,  they  obtain  the 
quality  of  shining  after  they  have  been  exposed  to  the 
light.  The  brief  flash  of  an  electric  spark  is  sufficient  to 
make  them  glow  splendidly ;  but,  what  is  very  singular, 
the  rays,  which  in  this  instance  bring  about  this  result, 
can  not  pass  through  a  piece  of  glass.  Glass  is  perfectly 
opaque  to  them.  We  can  not  regard  that  as  light  which 
is  unable  to  pass  through  glass  ;  and  on  arguments  of  this 
character,  I  have  shown  that  the  phosphorogenic  rays  are 
entitled  to  be  regarded  as  a  distinct  imponderable  prin- 
ciple.— (Phil.  Mag.,  Aug.,  1844.) 


LECTURE  XIX. 

WAVE  THEORY  OF  LIGHT. — Fixed  Lines  in  the  Solar 
Spectrum. — Proofs  of  the  Existence  of  the  Ether. — Light 
consists  of  Waves  in  it.— The  Ethereal  Particles  move 
but  little. — Distinction  between  Vibration  and  Undula- 
tion. —  FresneVs  Theory  of  Transverse  Vibrations.  — 
Transverse  and  Normal  Waves. — Brilliancy  of  Light 
depends  on  Amplitude  'of  Vibration. 

IN  the  foregoing  examination,  we  have  found  that  light 
is  very  far  from  being  a  simple  agent ;  it  contains  at  least 
four  distinct  principles  :  heat,  light,  chemical  action,  and 
phosphorescence  ;  but  of  each  of  these  there  are  many 
modifications.  The  eye  proves  to  us  that  of  light  there 
exist  at  least  seven  different  varieties,  answering  to  the 
seven  colors,  and  besides  this,  innumerable  intermediate 
tints ;  the  same  subdivision  may  be  traced  for  each  of  the 
other  principles. 

When  the  aperture  which  admits  a  ray  of  light  into  the 
dark  room",  Fig.  56,  is  a  narrow  fissure  or  slit,  not  more 

"What  proof  is  there  of  the  existence  of  a  fourth  principle  ?  Can  the 
phosphorogenic  rays  of  an  electric  spark  pass  through  glass  ?  Are  there 
any  subsidiary  modifications  besides  the  four  here  mentioned  ? 


WAVE    THEORY    OF    LIGHT.  79 

than  the  one  thirtieth  of  an  inch  in  width,  the  spec- 
trum which  is  formed  by  the  action  of  a  prism  is 
crossed  by  great  numbers  of  black  lines.  These 
always  are  found  in  the  same  position,  as  respects 
the  colored  spaces,  and,  from  the  invariability  of 
that  position,  are  much  used  as  boundary  marks. 
They  are  designated  by  the  letters  of  the  alpha- 
bet, and  their  relative  magnitude,  with  their  po- 
sition, is  given  in  Fig.  59. 

It  has  already  been  said  that  the  cause  of  light 
is  an  undulatory  movement  taking  place  in  the 
ethereal  medium.  That  such  a  medium  exists 
throughout  all  space,  seems  to  be  proved  by  a 
number  of  astronomical  facts.  It  exerts-  a  resist- 
ing agency  on  bodies  moving  in  it.  From  its 
tenuity,  we  should  scarcely  expect  that  it  would 
impress  any  disturbance  on  the  great  planetary  masses ; 
but  on  light  gaseous  cometary  bodies  it  produces  a  per- 
ceptible action.  The  comet  of  Encke,  with  a  period  of 
about  1200  days,  is  accelerated  in  each  revolution  by 
about  two  days  ;  and  that  of  Biela,  with  a  period  of  2460 
days,  is  accelerated-  by  about  one  day.  As  there  is  no 
other  obvious  cause  for  these  results,  astronomers  have 
erally  looked  upon  them  as  corroborative  proofs 
istence  of  a  resisting  medium,  that  universal  ether 
to  which  so  many  other  facts  point. 

In  this  elastic  medium,  undulatory  movements  can  be 
propagated  in  the  same  manner  as  waves  of  sound  in  the 
air.  It  is  to  be  clearly  understood  that  the  ether  aiM  light 
are  distinct  things  ;  the  latter  is  merely  the  effect  of  move- 
ments in  the  former.  Atmospheric  air  is  one  thing,  and 
the  sound  which  traverses  it  another.  The  air  is  not 
made  up  of  the  notes  of  the  gamut,  nor  is  the  ether  com  • 
posed  of  the  seven  colors  of  light.  , 

Across  the  ether,  undulatory  movements,  resembling,  in 
many  respects,  the  waves  of  sound  in  the  atmosphere,  trav- 
erse with  prodigious  velocity.  From  the  eclipses  of  Ju- 
piter's satellites,  and  other  astronomical  phenomena,  it 
appears  that  the  rate  of  the  propagation  of  light,  or  the 

What  are  the  fixed  lines  ?  How  are  these  lines  designated,  and  .what 
is  their  use  1  What  proofs  have  we  of  the  existence  of  an  ethereal  me- 
dium ?  What  is  the  relation  between  the  ether  and  light  ?  At  what 
rate  is  light  propagated  7 


very  gene 
of  the  existe 


80 


MECHANISM    OF    WAVES. 


f  60> 


velocity  with  which  these  waves  advance,  is  195,000  miles 
in  a  second.  We  are  not,  however,  to  understand  by  this 
that  the  ethereal  particles  rush  forward  in  a  rectilinear 
course  at  that  rate  :  those  particles,  far  from  advancing, 
remain  stationary. 

If  we  take  a  long  cord,  a  b,  Fig.  60,  and  having  fast- 

ened  it  by  the  extrem- 
ity, b,  to  a  fixed  obsta- 
cle, commence  agita- 
ting the  end,  0,  up  and 
down,  the  cord  will  be 
thrown  into  wave-like  motions  passing  rapidly  from  one 
end  to  the  other.  This  may  afford  us  a  rude  idea  of  the 
nature  of  the  ethereal  movements.  The  particles  of  which 
the  cord  is  composed  do  not  advance  or  retreat,  though 
the  undulations  are  rapidly  passing. 

So,  too,  if  in  the  center,  c,  of  a  surface  of  water,  Fig. 
Fig.  61.  61,  we  make  a  tapping  motion  with  the 

finger,  circular  waves  are  propagated, 
which,  expanding  as  they  go,  soon  reach 
the  sides  of  the  vessel  which  holds  the 
water.  A  light  object  placed  on  the 
suiface  is  not  violently  drifted  forward 
by  the  waves,  but  remains  entirely  mo- 
tionless. We  see,  therefore,  that  there 
is  a  wide  distinction  between  the  mo- 
tion of  a  wave  and  the  motions  of  the  particles  among 
which  it  is  passing.  They  retain  their  places,  but  the 
wave  flows  rapidly  forward. 

A  distinction  is  to  be  made  between  the  words  vibra- 
tion and  undulation.  In  the  case  of  the  cord,  Fig.  60,  the 
vibration  is  represented  by  the  movement  exerted  by  the 
hand  at  the  free  extremity,  a  ;  the  undulation  is  the  wave 
like  motion  that  passes  along  the  cord.  In  the  case  of 
the  water,  Fig.  61,  the  vibration  was  represented  by  the 
tapping  motion  of  the  finger,  the  undulation  by  the  result- 
ing wave.  We,  therefore,  see  that  these  stand  in  the  re- 
lation of  cause  and  effect  :  the  vibration  is  the  cause,  and 
the  undulation  the  effect.  Throughout  the  ethereal  medi- 

Do  the  ethereal  particles  move  forward  at  that  rate  ?  How  may  the 
movements  of  ethereal  waves  be  represented  by  a  cord  ?  How  may  they 
be  represented  on  the  surface  of  water  ?  Do  the  vibrating  particles  move 
forward  with  the  wave  ?  What  is  the  distinction  between  vibrationi  and 
undulations  ? 


THEORY    OF    TRANSVERSE    VIBRATIONS.  81 

urn,  each  particle  vibrates  and  transmits  the  undulatory 
effect  to  the  particles  next  beyond  it. 

In  the  same  way  as  a  vibrating  cord  agitates  the  sur- 
rounding air,  and  makes  waves  of  sound  pass  through  it, 
so  does  an  incandescent  or  shining  particle,  vibrating  with 
prodigious  rapidity,  impress  a  wave-like  movement  on  the 
ether,  and  the  movement  eventually  impinging  on  the  eye 
is  what  we  call  light. 

To  refer  again  to  the  simple  illustration  given  in  Fig. 
60  :  it  is  obvious  that  there  are  an  infinite  variety  of  di- 
rections in  which  we  may  vibrate  that  cord  or  throw  it 
into  undulations.  We  may  move  it  up  and  down,  or 
horizontally  right  and  left,  and  also  in  an  infinite  number 
of  intermediate  directions,  every  one  of  which  is  trans- 
verse, or  at  right  an-  Fig.  62. 
gles  to  the  length  of 
the  cord,  as  a  a,  b  b, 
c  c,  &c.,  Fig.  62. 
This  is  the  peculiari- 
ty of  the  movement 
of  light.  Its  vibrations  are  transverse  to  the  course  of  the 
ray;  and  in  this  it  differs  from  the  movement  of  sound,  in 
which  the  vibrations  are  normal,  that  is  to  say,  executed  in 
the  direction  of  the  resulting  wave,  and  not  at  right  angles 
to  it. 

This  great  discovery  of  the  transverse  vibrations  of 
light  was  made  by  M.  Fresnel.  It  is  the  foundation  of 
the  whole  theory  of  optics,  and  offers  a  simple  but  brill- 
iant explanation  of  so  many  of  the  phenomena  of  light, 
that  the  undulatory  theory  is  by  many  writers  designated 
the  THEORY  OP  TRANSVERSE  VIBRATIONS. 

It  may,  however,  be  remarked,  that  though  light  con- 
sists of  rays  originating  in  these  transverse  motions,  it  is 
not  impossible  that  there  may  be  other  phenomena  which 
correspond  to  movements  in  other  directions.  To  those 
movements  our  eyes  are  totally  blind,  and  hence  we  can 
not  speak  of  them  as  light.  In  the  same  way  there  may 
be  motions  in  the  air,  due  to  transverse  vibrations,  but  to 
them  our  ear  is  perfectly  deaf.  But  it  is  not  improbable 
that  God  has  formed  organs  of  vision  and  organs  of  hear- 


How  does  each  ethereal  particle  propagate  the  wave  to  those  beyond 

?    Is  there  any  analogy  between  sound  and  lig" 
__iay  a  cord  be  vibrated  ?     What  is  implied  by 
verse  vibrations  ?    Are  other  motions  possible  ? 


it?    Is  there  any  analogy  between  sound  and  light?    In  how  many  ways 
may  a  cord  be  vibrated  ?     What  is  implied  by  the  term  theory  of  trails- 


82  COLORS    DEPEND    ON    WAVE-LENGTH. 

ing  in  the  case  of  other  animals  upon  a  different  type  ; 
eyes  that  can  perceive  normal  vibrations  in  the  ether, 
and  ears  that  can  distinguish  transverse  sounds  in  the  air. 
Lights  differ  from  each  other  in  two  striking  particulars 
— brilliancy  and  color.  These  are  determined  by  certain 
affections  or  qualities  in  the  waves.  On  the  surface  of 
water  we  may  have  a  wave  not  an  inch  in  altitude,  or  a 
wave,  as  the  phrase  is,  "  mountains  high."  Under  these 
circumstances,  waves  are  said  to  differ  in  amplitude  ;  and, 
transferring  this  illustration  to  the  case  of  light,  a  wave, 
the  amplitude  of  which  is  great,  impresses  us  with  a  sense 
of  intensity  or  brilliancy,  but  a  wave,  the  amplitude  of 
which  is  little,  is  less  bright.  The  brilliancy  of  light  de- 
pends on  the  magnitude  of  the  excursions  of  the  vibrating 
particle. 


LECTURE  XX. 

WAVE  THEORY  OP  LIGHT. —  Colors  of  Light  depend  upon 
W^ave    Lengths.  —  Interference   of  Sounds.  —  Young's 
Theory  of  Interference  of  Light. — Condition  of  Inter- 
ference.— Explanation  of  Lights  and  Shades  in  Shad- 
ows. 

BY  the  length  of  a  wave  upon  water,  we  mean  the  dis- 
tance that  intervenes  from  the  crest 
5  of  one  wave  to  that  of  the  next,  or 

from    depression    to    depression. 

c~  ~d  Thus,  in  Fig.  63,  from  a  to  £,  or, 

what  is  the  same,  from  c  to  d,  constitutes  the  wave  length. 

In  the  ether  the  length  of  the  waves  determines  the 
phenomenon  of  color;  this  may  be  rigorously  proved,  as 
we  shall  soon  see,  when  we  come  to  the  methods  by  which 
philosophers  have  determined  the  absolute  lengths  of  un- 
dulations. It  has  been  found  that  the  longer  waves  give 
rise  to  red  light,  the  shorter  ones  to  violet,  and  those  of 
intermediate  magnitudes  the  other  colors  in  the  order  of 
their  refrangibility. 

Two  rays  of  light,  no  matter  how  brilliant  they  are  sep- 

What  is  meant  by  the  amplitude  of  waves  ?  On  what  does  the  brillian. 
cy  of  light  depend  ?  What  is  meant  by  the  length  of  a  wave  1  What  is 
the  connection  between  color  and  wave  length  ? 


TWO   SOUNDS    PRODUCE    SILENCE.  83 

arately,  may  be  brought  under  such  relations  to  one 
another  as  to  destroy  each  others  effect  and  produce  dark- 
ness. Light  added  to  light  may  produce  darkness.  Two 
sounds  may  bear  such  a  relation  to  each  other  that  they 
shall  produce  silence ;  and  two  waves,  on  the  surface  of 
water,  may  so  interfere  with  one  another  that  the  water 
shall  retain  its  horizontal  position. 

Take  two  tuning  forks  of  the  same  note,  and  fasten  by 
a  little  sealing  wax  on  one  prong  of  each  a 
disc  of  card-board,  half  an  inch  in  diameter, 
as  seen  Fig.  64,  a.  Make  one  of  the  forks  a 
little  heavier  than  the  other,  by  putting  on 
the  end  of  it  a  drop  of  the  wax. 

Then  take  a  glass  jar,  b,  about  two  inches 
in  diameter  and  eight  or  ten  long,  and  having 
made  one  of  the  forks  vibrate,  hold  it  over 
the  mouth  of  the  jar,  as  seen  at  d,  its  piece 
of  card-board  being  downward  ;  commence  pouring  water 
into  the  jar,  and  the  sound  will  be  greatly  re-enforced. 
It  is  the  column  of  air  in  the  jar  vibrating  in  unison  with 
the  fork,  and  we  adjust  its  length  by  pouring  in  the  water; 
when  the  sound  is  loudest,  we  cease  to  pour  in  any  more 
water,  the  jar  is  adjusted,  and  we  can  now  prove  that  two 
sounds  added  together  may  produce  silence. 

It  matters  not  which  fork  is  taken,  whether  it  be  the 
light  or  the  loaded,  on  making  it  vibrate  and  holding  it 
over  the  mouth  of  the  resonant  jar,  we  hear  a  uniform 
and  clear  sound,  without  any  pause,  stop,  or  cessation. 
But  if  we  make  both  vibrate  over  the  jar  together,  a  re- 
markable phenomenon  arises,  a  series  of  sounds  alterna- 
ting with  a  series  of  silences  ;  for  a  moment  the  sound  in- 
creases, then  dies  away  and  ceases,  then  swells  forth 
again,  and  again  declines,  and  so  it  continues  until  the 
forks  cease  vibrating.  The  length  of  these  pauses  may  be 
varied  by  putting  more  or  less  wax  on  the  loaded  fork  ; 
and  as  we  can  see  that  even  during  the  periods  of  silence 
both  forks  are  rapidly  vibrating,  the  experiment  proves 
that  two  sounds  taken  together  may  produce  silence. 

Under  these  circumstances,  waves  of  sound  are  said  to 

\Vhat  is  meant  by  the  interference  of  lights  or  of  sounds  ?  Give  an  il- 
lustration of  the  interference  of  sounds.  What  is  the  character  of  the 
Bound  which  the  resonant  jar  emits  ?  Why  are  there  pauses  in  it  ?  At 
the  time  of  these  pauses,  are  the  forks  vibrating  ? 


84 


LAWS    OF    INTERFERENCE. 


Fig.  65. 


interfere  with  each  other,  and  in  like  manner  interference 
takes  place  among  the  waves  of  light.  We  can  gather 
an  idea  of  the  mechanism  by  considering  this  case  in  waves 
upon  water,  in  which,  if  two  undulations  encounter  under 
such  circumstances  that  the  concavity  of  the  one  corre- 
sponds with  the  convexity  of  the  other,  they  mutually  de- 
stroy each  other's  effect. 

If  two  systems  of  waves  of  the  same  length  encounter 
each  other  after  having  come  through  paths  of  equal  length, 
they  will  not  interfere.  Nor  will  they  interfere  even 
though  there  be  a  difference  in  the  length  of  these  paths, 
provided  that  difference  be  equal  to  one  whole  wave,  or 
two,  or  three,  &c. 

But  if  two  systems  of  waves  of  equal  length  encounter 
each  other  after  having  come  through  paths  of  unequal 
length,  they  will  interfere,  and  that  interference  will  be 
complete  when  the  difference  of  the  paths  through  which 
they  have  come  is  half  a  wave,  or  1-*-,  2£,  3^-,  £c. 

These  cases  are  respectively  shown 
at  a  I,  and  c  d,  Fig.  65,  at  the  point 
of  encounter,  x  ;  in  the  first  instance, 
the  two  sets  of  waves  are  in  the  same 
phase,  that  is,  their  concavities  and 
convexities  respectively  correspond, 
and  there  is  no  interference ;  but  in 
the  second  case,  at  the  point  of  en- 
counter, x,  the  two  systems  are  in  opposite  phases,  the 
convexity  of  the  one  corresponding  with  the  concavity  oi 
the  other,  and  interference  takes  place. 

Upon  these  principles,  we  can  account  for  the  remark- 
Fig.  66.  able  results  of  the  following  experi- 

ment:  From  a  lucid  point,  s,  Fig. 
66,  which  may  be  formed  by  the 
rays  of  the  sun  converged  by  a  dou- 
ble convex  lens  of  short  focus,  or  by 
passing  a  sunbeam  through  a  pin- 
hole,  let  rays  emanate,  and  in  them 
place  the  opaque  obstacle,  a  Z>,  which 
we  will  suppose  to  be  a  cylindrical 


When  two  waves  upon  water  encounter  each  other,  under  what  cir- 
cumstances will  they  interfere  ?  When  systems  of  waves  of  equal  length 
encounter  one  another,  when  do  they,  and  when  do  they  not,  interfere  7 
Describe  the  experiment  represented  in  Fig.  66. 


INTERFERENCE    OF   LIGHT.  85 

body,  seen  endwise  in  the  figure;  at  some  distance  beyond 
place  a  screen  of  white  paper,  c  d,  to  receive  the  shadow. 
It  might  be  supposed  that  this  shadow  should  be  of  a 
magnitude  included  between  x  y^  because  the  rays,  s  a, 
s  Z>,  which  pass  tfte  sides  of  the  obstacle  impinge  Fig  G7 
on  the  paper  at  those  points.  It  might  farther  be 
supposed,  that  within  the  space  x  y  the  shadow 
should  be  uniformly  dusky  or  dark  ;  but,  on  exam- 
ining it,  such  will  not  be  found  to  be  the  case. 
The  shadow  will  be  found  to  consist  of*  a  series  of 


light  and  dark  stripes,  as  represented  in  Fig.  67. 
In  its  middle,  at  e,  Figs.  66  and  67,  there  is  a  white 
stripe ;  this  is  succeeded  on  each  side  by  a  dark 
one ;  this,  again,  by  a  bright  one,  and  so  on  alternately. 

Upon  the  undulatory  theory,  all  this  is  readily  explain- 
ed. Sounds  easily  double  round  a  corner,  and  are  heard 
though  an  obstacle  intervenes.  Waves  upon  water  pass 
round  to  the  back  of  an  object  on  which  they  impinge, 
and  the  undulations  of  light  in  the  same  manner  flow 
round  at  the  back  of  the  piece  of  wire,  a  b,  Fig.  66  ;  and 
now  it  is  plain  that  two  series  of  waves  which  have  passed 
from  the  sides  of  the  obstacle  to  the  middle  of  its  shadow, 
that  is,  along  the  lines  a  e,  b  e,  have  gone  through  paths 
of  equal  length,  and,  therefore,  when  they  encounter  at 
the  point  e,  they  will  not  interfere,  but  exalt  each  other's 
effect. 

But,  leaving  this  central  point,  e,  and  passing  to^  it  is 
plain  that  the  systems  of  waves  which  have  come  through 
the  paths  af,  bf,  have  come  through  different  distances, 
for  bfis  longer  than  a  f;  and  if  this  difference  be  equal 
to  the  length  of  half  a  wave,  they  will,  when  they  encoun- 
ter at  the  pointy,  interfere  and  destroy  each  other,  and  a 
dark  stripe  results. 

Beyond  this,  at  the  point  g,  the  waves  from  each  side 
of  the  obstacles,  ft  g,  b  g,  again  have  come  through  une- 
qual paths  ;  but,  if  the  difference  is  equal  to  the  length  of 
one  whole  wave,  they  will  not  interfere,  and  a  white 
stripe  results. 

Reasoning  in  this  manner,  we  can  see  that  the  interioi 

Is  the  resulting  shadow  uniformly  dark  ?  At  the  central  point  of  the 
shadow,  is  it  dark  or  light  ?  Explain  the  cause  of  this  central  light  space, 
and  of  the  alternate  dark  and  light  ones  on  each  side  of  it  ?  "What  is  the 
length  of  the  paths  of  the  waves  which  go  to  the  illuminated  spaces,  and  of 
those  which  go  to  the  dark  ones  ? 

H 


86  LENGTH    OF    WAVES. 

of  such  a  shadow  consists  of  illuminated  and  dark  spaces 
alternately  :  illuminated  spaces,  when  the  light  has  come 
through  paths  that  are  equal,  or  that  differ  from  each  oth- 
er by  1,  2,  3,  4,  .  .  &c.,  waves;  and  dark,  when  the  dif- 
ference between  them  is  equal  to  ^,  1^,  2|,  3^,  .  .  &c., 
waves. 

That  it  is  the  interference  of  the  light  coming  from  the 
opposite  sides  of  the  opaque  object  which  is  the  cause  of 
these  phenomena,  is  proved  by  the  circumstance  that  if 
we  place  an  opaque  screen  on  one  side  of  the  obstacle,  so 
as  to  prevent  the  light  passing,  the  fringes  all  disappear. 


LECTURE  XXL 

WAVE  THEORY  OF  LIGHT. — Measurement  of  the  Length  of 
a  Wave  of  Light.- — Length  differs  for  different  Colors. 
— Measurement  of  the  Period  of  Vibrations. — Nature  of 
Polarized  Light.  —  Plane,  Circular,  and  Elliptical 
Polarized  Light. — Reflection,  Refraction,  and  Absorp- 
tion of  Light. 

THE  experiment,  Fig.  66,  may  enable  us  to  determine 
the  length  of  a  wave  of  light.  This  may  be  readily  done 
by  measuring  the  distances  af  and  bf,  or  from  the  sides 
of  the  obstacle  to  the  first  bright  stripe  from  the  central 
one,  for  at  that  point  the  difference  between  those  two 
lines,  a  f  and  b  f,  is  equal  to  the  length  of  one  wave. 
We  might  employ  the  second  bright  stripe  ;  the  differ- 
ence then  would  be  equal  to  two  waves. 

Farther,  if,  instead  of  using  ordinary  white  light,  radia- 
ting from  the  lucid  point,  s,  we  use  colored  lights,  such  as 
red,  yellow,  blue,  &c.,  in  succession,  we  shall  find  that 
the  wave  length  determined  by  the  process  just  explained 
differs  in  each  case ;  that  it  is  greatest  in  red,  and  small- 
est in  violet  light.  By  exact  experiments  made  upon 
methods  more  complicated  than  the  elementary  one  here 
given,  it  has  been  found  that  the  different  colored  rays  of 
light  have  waves  of  the  following  length  : 

How  can  it  be  proved  that  the  waves  from  the  opposite  sides  of  the  ob- 
stacle interfere  ?  How,  by  this  arrangement,  might  we  measure  the 
length  of  a  wave  of  light?  When  different  colors  oflight  are  used,  are 
the  waves  found  to  be  of  equal  length  ? 


FREQUENCY    OF    WAVE-VIBRATION.  87 

WAVE    LENGTHS    OF    THE    DIFFERENT    COLORS    OF    LIGHT. 

The  English  inch  is  supposed  to  be  divided  into  ten 
millions  of  equal  parts,  and  of  those  parts  the  wave  lengths 
are  : 


For  red  light  . 
"  orange  . 
"  yellow  . 
"  green .  . 

In  this  manner,  it 


256 
240 
227 
211 


For  blue 196 

"     indigo 185 

"    violet  .  .    .  174 


is  proved  that  the  different  colors  of 
light  arise  in  the  ether,  from  its  being  thrown  into  waves 
of  different  lengths. 

Knowing  the  rate  at  which  light  is  propagated  in  a 
second,  and  the  wave  length  for  a  particular  color,  we  can 
readily  tell  the  number  of  vibrations  executed  in  a  second, 
for  they  plainly  are  obtained  by  dividing  195,000  miles, 
the  rate  of  propagation  by  the  wave  length.  From  this  it 
appears,  that  if  a  single  second  of  time  be  divided  into  one 
million  of  equal  parts,  a  wave  of  red  light  trembles  or  pul- 
sates 458  millions  of  times  in  that  inconceivably  short  in- 
terval, and  a  wave  of  violet  light  727  millions  of  times. 

In  speaking  of  the  constitution  of  matter,  in  Lectures  I. 
and  II.,  I  had  occasion  to  allude  to  the  amazingly  minute 
scale  on  which  it  is  constructed.  The  remarkable  facts 
we  are  now  considering  are  a  monument  to  the  genius  of 
Newton  and  his  successors,  for  they  give  us  a  just  idea  of 
the  scale  of  space  and  time  upon  which  Nature  carries  on 
her  works  among  the  molecules  of  matter. 

Common  light,  as  has  been  said,  originates  in  vibratory 
motions  taking  place  in  every  direction  transverse  to  the 
ray.  With  polarized  light  it  is  different;  to  gather  an 
idea  of  the  nature  of  polarized  light,  we  must  refer  once 
more  to  the  cord,  Fig.  62,  which,  as  has  been  said,  serves 
to  imitate  common  light  when  its  extremity  is  vibrated 
vertically,  horizontally,  and  in  all  intermediate  positions 
in  rapid  succession.  But  if  we  simply  vibrate  it  up  and 
down,  or  right  and  left,  then  it  imitates  polarized  light; 
polarized  light  is,  therefore,  caused  by  vibrations  trans- 
verse to  the  ray,  but  which  are  executed  in  one  direction 
only. 

What  is  the  length  of  a  wave  of  red  and  of  violet  light  respectively? 
How  can  we  ascertain  the  number  of  vibrations  in  a  second  ?  On  the  un- 
dulatory  theory,  in  what  directions  do  the  ethereal  particles  vibrate  in  the 
case  of  common  light  ?  What  is  the  case  in  polarized  light  ? 


88  POLARIZATION    OF    LIGHT. 

There  is  a  certain  gem,  the  tourmaline,  which  serves  to 
Fig.  68.  exhibit  the  properties  of  polar- 

ized light.  If  we  take  a  thin 
plate  of  this  substance,  c  d,  prop- 
erly cut  and  polished,  and  allow 
a  ray  of  light,  a  b,  Fig.  68,  to 
fall  upon  it,  that  ray  will  be 
freely  transmitted  through  a  second  plate  if  it  be  held 
symmetrically  to  the  first,  as  shown  at  ef;  Hut  if  we  turn 
the  second  plate  a  quarter  round,  as  seen  at  g  k,  then  the 
light  can  not  pass  through.  The  rays  of  the  meridian  sun 
can  not  pass  through  a  pair  of  crossed  tourmalines. 

Fi    69  The  cause  of  this  is  obvious:  if  we  take 

a  thin  lath  or  strip  of  pasteboard,  c  d, 
Fig.  69,  and  hold  it  before  a  cage,  or 
grate,  a  b,  it  will  readily  slip  through 
when  its  plane  coincides  with  the  bars  ; 
but  if  we  turn  it  a  quarter  round,  as  at  e 
f,  then  of  course  it  can  not  pass  the  bars. 
Now  the  plate  of  tourmaline,  Fig.  68,  c  d,  polarizes  the 
light,  a  b,  which  falls  upon  it ;  that  is,  the  waves  that  pass 
through  it  are  vibrating  all  in  one  plane.  They  pass, 
therefore,  readily  through  a  second  plate  of  the  same  kind, 
so  long  as  it  is  held  in  such  a  way  that  its  structure  coin- 
cides with  that  motion,  but  if  it  be  turned  round  so  as  to 
cross  the  waves,  then  they  are  unable  to  pass  through  it. 
There  are  many  ways  in  which  light  can  be  polarized : 
by  reflection,  refraction,  double  refraction,  &c.  The  re- 
sulting motion  impressed  on  the  ether  is  the  same  in  all 
cases. 

Light  modified  as  just  described  is  designated  plane 
polarized  light ;  but  there  are  other  varieties  of  polariza- 
tion. If  the  end  of  the  rope,  Fig.  62,  be  moved  in  a  cir- 
cle, circular  waves  will  be  produced,  imitating  circularly 
polarized  light;  and  if  it  be  moved  in  an  ellipse,  elliptical 
polarized  light. 

The  undul&tory  theory  of  light  gives  a  clear  account  of 
the  ordinary  phenomena  of  optics.  The  general  law 
under  which  light  is  reflected  from  polished  surfaces  is  a 

Describe  the  optical  properties  of  the  tourmaline.  Give  an  illustration 
of  the  phenomenon.  What  is  the  cause  of  the  action  of  the  second  tour 
maline  plate  ?  Mention  some  of  the  methods  by  which  light  may  be  po- 
larized. What  is  circularly  polarized  light  ?  What  is  ellipticaliy  polar 
ized  lisrht  ? 


LAWS  OF  REFLECTION  AND  REFRACTION.      89 

direct  consequence  of  it ;  that  law  is :  that  the 
angle,  d  c  b,  Fig.  70,  made  by  the  reflected  V* 
ray,  d  c,  with  a  perpendicular,  c  b,  drawn  to    \ 
the  point  c,  at  which  the  light  impinges,  is 
equal  to  the  angle,  a  c  b,  which  the  incident 
ray  makes  with  the  same  perpendicular,  or, 
as  it  is  briefly  expressed,  "  the  angles  of  inci- 
dence and  reflection  are  equal  to  each  other,  and  on  op- 
posite sides  of  the  perpendicular." 

By  the  aid  of  this  law,  we  can  show  the  action  of  re- 
flecting surfaces  of  any  kind,  and  discover  the  properties 
of  plane  and  curved  mirrors,  whether  they  be  concave  or 
convex,  spherical,  elliptical,  paraboloidal,  or  any  other 
figures. 

From  the  undulatory  theory,  the  law  of  the  refraction 
of  light  also  follows  as  a  necessary  consequence.  It  is  : 
in  every  transparent  substance,  "  the  sines  of  'the  angles 
of  incidence  and  refraction  are  to  each  other  in  a  constant 
ratio ;"  and  by  the  aid  of  this  law  we  can  determine  the 
action  of  media  bounded  by  surfaces  of  any  kind,  plane  or 
spherical,  concave  or  convex.  It  explains  the  action  of 
lenses,  and  the  construction  of  refracting  telescopes  and 
microscopes. 

Sir  Isaac  Newton's  discovery,  that  white  light  arises 
from  the  mixture  of  the  different  colored  rays  in  certain 
proportions,  explains  the  cause  of  the  colors  which  trans- 
parent media  often  exhibit;  thus,  if  glass  be  stained  with 
the  oxide  of  cobalt,  it  allows  a  blue  light  to  pass  it,  and 
upon  such  principles  the  art  of  painting  on  glass  depends ; 
different  colors  being  communicated  by  different  metallic 
oxides.  The  cause  of  this  effect  is  readily  discovered  ; 
for,  if  we  make  the  light  which  enters  a  dark  room,  as  in 
Fig.  56,  pass  through  such  a  piece  of  stained  glass  before 
it  goes  through  the  prism,  and  examine  the  resulting  spec- 
trum, we  find  that  several  rays  are  wanting  in  it ;  that  the 
glass  has  absorbed  or  detained  some,  and  allowed  others 
to  traverse  it.  A  piece  of  blue  glass  thus  suffers  most  of 
the  blue  light  to  pass,  but  stops  the  green,  the  yellow,  &c. 
But  it  is  also  to  be  observed,  that  the  light  which  is  trans- 
mitted by  any  of  these  colored  media  is  not  pure,  it  is 

"What  is  the  general  Taw  of  reflection?  What  is  the  law  of  the  refrac- 
tion of  light  ?  What  is  the  cause  of  the  colors  of  transparent  media  ?  If 
the  light  transmitted  through  these  colored  media  pure  ? 


90  THE   TITHQNIC  RAYS. 

contaminated  with  other  tints  ;  the  blue  glass,  for  instance, 
does  not  stop  all  the  rays  except  the  blue  ;  it  allows  a  large 
portion  of  the  red  to  pass,  and  hence  the  light  it  transmits 
is  more  or  less  compound. 


LECTURE  XXII. 

THE  TITHONIC  RAYS. — Peculiarities  of  ike  Tithonic  Rays. 
—  Their  Physical  Independence  of  Heat  and  Light. — 
Analogies  with  Light. — Found  in  Moonlight,  Lamp- 
light^ Sfc. — Preliminary  Absorption  and  definite  Action. 
— In  producing  a  Chemical  Effect,  tlic  Ray  changes. — 
Daguerreotype. — Application  to  taking  Portraits. — Na- 
ture of  the  Daguerreotype. — Other  Photogenic  Processes. 

IT  has  been  already  observed,  that  when  a  solar  spec- 
trum falls  upon  paper  covered  over  with  chloride  of  sil- 
ver, the  chloride  turns  black  in  the  more  refrangible  re- 
gions, and  from  this  and  similar  experiments  we  have  been 
led  to  the  knowledge  that  there  exists  in  the  sunbeam  a 
principle  which  can  bring  about  chemical  changes. 

This  fact  has  been  received  from  the  beginning  of  the 
present  century;  but,  of  late,  much  attention  has  been 
given  to  these  rays,  and  from  a  consideration  of  the  phe- 
nomena they  exhibit,  I  have  endeavored  to  prove  that  they 
constitute  a  fourth  imponderable  principle  of  the  same 
rank  as  heat,  light,  and  electricity ;  and,  for  the  purpose 
of  giving  precision  to  this  view,  have  proposed  that  they 
should  be  called  Tithonic  rays,  from  the  circumstance 
that  they  are  always  associated  with  light ;  drawing  the 
allusion  from  the  classical  fable  of  Tithonus  and  Aurora. 

This  name  is,  however,  to  be  regarded  as  a  provisional 
one.  Every  thing  seems  to  indicate  that  sooner  or  later 
all  these  principles  will  be  reduced  to  one  of  a  more  gen- 
eral nature,  or  that  they  are  all  modifications  of  move- 
ments taking  place  in  the  ether. 

The  evidence  of  the  physical  independence  of  the  Ti- 
thonic rays  is  very  much  of  the  same  character  as  the  evi- 
dence of  the  difference  between  heat  and  light.  These 

What  reason  have  we  to  suppose  that  there  exists  another  principle 
besides  heat  and  light  in  the  solar  rays  ?  Why  is  the  name  Tithonic  rays 
suggested  for  this  principle  ? 


PROPERTIES    OF    THE    TITHONIC    RAYS.  91 

rays  are  invisible  to  the  eye,  and  therefore  are  not  light ; 
they  do  not  affect  a  thermometer,  and  therefore  are  not 
heat.  Media  which  are  transparent  to  heat  are  not  trans- 
parent to  them,  and  media  through  which  light  readily 
passes  are  perfectly  opaque  to  them. 

The  Tithonic  rays  are  emitted,  and  undergo  reflection, 
refraction,  and  polarization,  precisely  in  the  manner  of 
light  and  heat.  Unlike  the  latter  principle,  they  exhibit 
no  phenomenon  of  conduction  ;  the  effect  which  they  pro- 
duce does  not  pass  from  particle  to  particle,  but  is  limited 
to  that  on  which  the  light  has  impinged  ;  nor  is  it,  as  yet, 
distinctly  established  that  they  exhibit. any  phenomenon 
analogous  to  secondary  radiation.  An  object  upon  which 
rays  of  heat  fall,  as  it  becomes  warm,  radiates  back  again, 
but  a  substance  on  which  Tithonic  rays  are  impinging 
does  not  radiate  in  like  manner. 

In  the  sunbeams  Tithonic  rays  exist  abundantly;  1  have 
also  found  them  in  the  moonlight,  in  sufficient  quantity  to 
give  copies  of  that  satellite  on  sensitive  surfaces.  In 
lamplight  and  other  artificial  light,  they  also  occur  to  a 
much  greater  extent  than  is  commonly  supposed.  They 
do  not  effect  a  thermometer,  because,  except  under  pe- 
culiar circumstances,  they  can  not  produce  expansion  ; 
their  office  appears  to  be  to  arrange  and  group  the  mole- 
cules of  bodies,  and  to  bring  about  the  substitution  of  one 
element  for  another. 

When  the  Tithonic  rays  fall  upon  a  sensitive  medium 
for  a  brief  space  of  time,  no  change  takes  place  in  it ; 
during  this  time  the  rays  are  actively  absorbed,  but  as 
soon  as  that  preliminary  absorption  is  over  they  act  in  a 
manner  which  is  perfectly  definite :  if,  for  instance,  it  be 
a  decomposition  they  are  bringing  about,  the  amount  of 
decomposing  effect  will  be  precisely  proportional  to  the 
quantity  of  rays  absorbed. 

When  a  beam  from  any  shining  source  causes  a  de- 
composing effect,  it  is  uniformly  observed  that  it  is  itself 
disturbed ;  the  medium  which  is  changing  impresses  a 
change  on  the  ray.  Thus,  a  mixture  of  chlorine  and  hy- 

Are  these  rays  visible  ?  Do  they  affect  a  thermometer?  Can  they  he 
conducted  like  heat?  Do  they  exhibit  secondary  radiation?  Are  they 
found  in  the  moonbeams  and  artificial  lights  ?  Do  they  affect  the  ther- 
mometer ?  The  mode  of  action  of  these  rays  on  bodies  is  divided  into  two 
stages,  what  are  they  ?  Does  the  ray  itself  change  in  bringing  about  these 


92  THE    DAGUERREOTYPE. 

drogen  unites  under  the  influence  of  a  ray,  but  that  por- 
tion of  the  ray  which  passes  through  the  mixture  has  lost 
the  quality  of  ever  bringing  about  a  like  change  again ; 
the  mixture  is  tithonized  and  the  light  detithonized. 

When  a  beam  from  any  shining  source  falls  on  a 
changeable  medium,  a  portion  of  it  is  absorbed  for  the 
purpose  of  effecting  the  change,  and  the  residue  is  either 
reflected  or  transmitted,  and  is  perfectly  inert  as  respects 
the  medium  itself. 

No  chemical  effect  can,  therefore,  be  produced  by  such 
rays  except  they  be  absorbed.  It  is  for  this  reason  that 
water  is  never  decomposed  by  the  sunshine,  nor  oxygen 
and  hydrogen  made  to  unite ;  for  these  substances  are  all 
transparent,  and  allow  the  rays  to  pass  without  any  ab- 
sorption, and  absorption  is  absolutely  necessary  before 
chemical  action  can  ensue. 

But  with  chlorine  the  case  is  very  different.  This  sub- 
stance exerts  a  powerful  absorbent  action  on  light ;  the 
effect  takes  place  on  the  more  refrangible  rays;  when 
mixed  with  hydrogen  and*set  in  the  light,  it  unites  with  a 
violent  explosion. 

The  process  of  the  Daguerreotype  depends  on  the  action 
of  the  Tithonic  rays.  It  is  conducted  as  follows  :  A  piece 
of  silver  plate  is  brought  to  a  high  polish  by  rubbing  it 
with  powders,  such  as  Tripoli  and  rotten-stone,  every  care 
being  taken  that  the  surface  shall  be  absolutely  pure  and 
clean,  a  condition  obtained  in  various  ways  by  different 
artists,  as  by  the  aid  of  alcohol,  dilute  nitric  acid,  &c. 
This  plate  is  next  exposed  in  a  box  to  the  vapor  which 
rises  from  iodine  at  common  temperatures,  until  it  has  ac- 
quired a  golden  yellow  tarnish  ;  it  is  next  exposed,  in  the 
camera  obscura,  to  the  images  of  the  objects  it  is  designed 
to  copy,  for  a  suitable  space  of  time.  On  being  removed 
from  the  instrument,  nothing  is  visible  upon  it ;  but  on  ex- 
posing it  to  the  fumes  of  mercury,  the  images  slowly  evolve 
themselves. 

To  prevent  any  farther  change,  the  tarnished  aspect  of 
the  plate  is  removed  by  washing  the  plate  in  a  solution  of 
hyposulphite  of  soda,  and  finishing  the  washing  with  wa- 
ter ;  it  can  then  be  kept  for  any  length  of  time. 

Does  the  ray  undergo  absorption  ?  "Why  can  not  water  be  decomposed 
in  the  sunshine  ?  Why  do  chlorine  and  hydrogen  explode  ?  Describe 
the  process  of  the  Daguerreotype.  Are  the  images  visible  at  first  ?  By 
what  means  are  they  brought  out  ?  How  is  the  picture  preserved  from 
farther  change  ? 


PHOTOGENIC    PORTRAITS.  93 

Several  important  improvements  on  the  original  process 
have  been  made:  1st,  by  exposing  the  plate,  after  it  has 
been  iodized,  to  the  vapor  of  bromine,  or  chloride  of  iodine, 
which  gives  it  a  wonderful  sensibility  ;  2d,  by  gilding  the 
plate,  after  the  other  operations  are  complete,  by  the  aid 
of  a  mixture  of  hyposulphite  of  soda  and  chloride  of  gold  ; 
this  acts  like  a  varnish,  fastening  the  picture  and  giving 
it  a  more  agreeable  yellow  tone. 

The  art  of  taking  portraits  from  the  life,  which  has  now 
become  a  branch  of  industry,  was  invented  by  me  soon 
after  the  Daguerreotype  was  known  in  America ;  at  that 
time,  this,  which  is  by  far  the  most  valuable  application 
of  the  chemical  agencies  of  light,  was  looked  upon  in  Eu- 
rope as  entirely  beyond  the  powers  of  this  process ;  but 
subsequently  great  improvements  in  it  have  been  made. 
My  memoir  descriptive  of  the  art  may  be  seen  in  the  Lon- 
don and  Edinburgh  Philosophical  Magazine  (September, 
1840),  and  the  facts  are  also  specified  in  the  Edinburgh 
Review  (January,  1843),  in  which  the  discovery  is  attrib- 
uted to  its  proper  source,  the  author  of  this  book. 

When  a  beam  falls  upon  the  surface  of  a  Daguerreotype 
plate,  it  communicates  to  the  iodide  of  silver  a  tendency 
to  decomposition,  but  iodine  is  never  set  free  because  of 
the  metallic  silver  behind.  On  exposing  a  surface  dis- 
turbed in  this  manner  to  the  vapors  of  mercury,  entire 
decomposition  of  the  iodide  ensues,  its  silver  unites  with 
the  mercury,  forming  a  white  amalgam,  and  the  iodine 
corrodes  the  metallic  silver  behind.  The  utmost  care 
must  be  taken  in  all  Daguerreotype  processes  to  have  no 
vapors  of  iodine,  or  bromine,  or  chlorine  about  the  camera 
or  other  apparatus ;  they  possess  the  quality  of  effacing 
the  effects  of  light,  and  the  most  common  source  of  failure 
among  Daguerreotype  artists  is  due  to  neglecting  this 
precaution. 

There  are  some  important  difficulties  to  which  the  Da- 
guerreotype is  liable.  For  taking  landscapes  it  is  not 
available.  Green  and  red  colors  impress  no  change  upon 
it.  The  order  of  colors  and  light  and  shadow  is  not,  there- 
fore, strictly  observed. 

Mention  some  of  the  later  improvements  of  the  process  ?  In  this  pro- 
cess is  iodine  set  free  from  the  plate  ?  With  what  does  the  iodine  unite 
under  the  influence  of  the  mercurial  vapor?  \Vliy  is  not  the  Daguerreo« 
type  applicable  to  landscapes  ? 


94  IDEAL    COLORATION. 

There  are  many  other  photogenic  processes  now  known : 
several  have  been  invented  by  Mr.  Talbot ;  among  them 
may  be  mentioned  the  calotype.  Sir  J.  Herschel,  also, 
has  discovered  very  beautiful  ones,  and  these  possess  the 
great  advantage  over  Daguerre's  that  they  yield  pictures 
upon  paper.  In  minuteness  of  effect  they  can  not.  howev- 
er, be  compared  to  the  Daguerreotype. 


LECTURE  XXIII. 

THEORY  OF  IDEAL  COLORATION. — Imaginary  Coloration. 
—  Variation  in  the  Colors  of  radiant  Heat  as  the  Temper- 
ature changes. — Ideal  Coloration  of  natural  Objects. — 
Fixed  Lines  in  the  Spectrum. — Phosphorogenic  Rays. — 
Relations  of  tJie  radiant  Principles  to  the  Vegetable 
World. — Spectral  Impressions. 

IN  explaining  the  discoveries  made  by  M.  Melloni  in 
relation  to  radiant  heat  (Lecture  XV.),  we  had  occasion 
to  observe  the  difference  between  the  action  of  glass  and 
rock  salt  in  their  quality  of  transparency,  and  it  was  stated 
that  the  phenomenon  is  due  to  differences  in  the  nature 
of  the  heat  analogous  to  the  different  colors  of  light.  As 
these  modifications  are  found  also  in  the  Tithonic  rays,  and 
as  neither  these  nor  the  rays  of  heat  are  visible  to  the  eye, 
I  have  suggested  the  use  of  the  term  ideal  or  imaginary 
coloration,  as  expressing  the  facts  we  have  now  under 
consideration. 

By  the  theory  of  ideal  coloration  we  mean,  that  as 
there  are  modifications  of  light  constituting  the  seven 
primitive  colors,  red,  orange,  yellow,  green,  blue,  indigo, 
and  violet,  so,  too,  there  are  similar  modifications  of  the 
other  invisible  principles  of  the  spectrum,  differing  from 
each  other  by  the  length  of  the  waves  which  constitute 
them  ;  and  also,  that  as  natural  bodies  exhibit  to  our 
eyes  a  variety  of  colors,  so,  in  the  same  manner,  they  are 
colored  as  respects  these  invisible  principles,  but  the  col- 
oration under  these  circumstances  is  different  from  their 
colorations  for  light. 

What  is  meant  by  ideal  coloration?  Do  natural  bodies  possess  cplora 
tion  for  tbe  other  principles  of  the  sunbeam  as  well  as  light  ?  Is  their  ool 
or  the  same  in  these  cases  ? 


IMAGINARY    COLORS    OF    BODIES.  95 

To  make  this  plain,  let  us  take  an  illustration :  glass 
is  colorless  and  transparent  to  light,  and  allows  any  kind 
of  light-ray  to  traverse  it  with  facility ;  but  to  heat,  com- 
ing from  sources  of  a  low  temperature,  it  is  wholly  opaque. 
And  this  arises  from  the  circumstance  that  the  rays  of  heat 
which  come  from  such  a  source  are  constituted  of  short 
waves,  and  therefore  bear  an  analogy  to  violet  light, 
while  glass  acts  toward  the  heat  as  a  ruddy  or  orange-col- 
ored medium.  The  reason,  therefore,  that  this  heat  of 
low  temperature  can  not  go  through  glass  is  because  it  is 
of  a  violet  color,  while  the  glass  is  red.  But  as  the  tem- 
perature rises,  calorific  rays  of  other  tints  begin  to  be 
emitted,  yellow  and  red  successively,  and  these  easily  find 
passage  through  the  medium. 

To  the  rays  of  heat,  rock  salt  is  a  white  body,  glass 
orange,  and  alum  deep  red.  The  color  of  these  bodies 
for  heat  is  not  the  same  as  their  color  for  light ;  and  as 
the  eye  can  not  detect  the  phenomenon  directly,  we  speak 
of  it  as  imaginary  or  ideal  coloration. 

Radiant  heat  undergoes  polarization  after  the  manner 
of  light ;  the  wave  mechanism  is  the  same  in  both  cases. 

The  Tithonic  rays,  also,  exhibit  all  the  phenomena  due 
to  imaginary  coloration,  and  they  may  therefore  be  spoken 
of  as  violet,  yellow,  green,  blue  Tithonic  rays.  To  them 
the  various  objects  of  nature  have  a  peculiar  coloration. 
The  bromide  of  silver  is  yellowish- white  as  respects  light, 
but  black  to  these  rays. 

As  respects  the  fixed  lines  discovered  in  the  luminous 
spectrum,  as  represented  in  Fig.  59,  they  also  occur  in 
the  impressions  left  upon  sensitive  surfaces  on  which  the 
spectrum  is  received,  as  was  discovered  by  M.  Bequerel 
and  myself  about  the  same  time  (1842).  In  this  instance, 
however,  they  are  far  more  numerous,  and  occur  in  groups 
of  many  hundreds  beyond  the  visible  limits  of  the  violet 
ray. 

It  has  already  been  mentioned  that  there  is  associated 
with  the  light  derived  from  shining  sources  an  invisible 
principle,  which  causes  the  phosphorescence  of  many 
bodies.  Thus,  if  oyster-shells  be  calcined  with  sulphur 

Why  does  glass  change  its  transparency  for  radiant  heat  ?  What  is 
the  color  of  rock  salt,  alum,  and  glass  for  heat  ?  Can  radiant  heat  be  po- 
larized? What  is  the  color  of  bromide  of  silver  for  light  rays  and  Ti- 
thonic rays  respectively  ?  Can  the  fixed  lines  be  obtained  on  sensitive 
(surfaces  ?  Give  some  instances  of  phosphorescent  bodies- 


96  PHOSPHORESCENCE. 

and  exposed  to  the  sun,  they  shine  for  a  considerable  time 
after  in  the  dark.  Nor  does  it  require  that  the  time  of 
exposure  should  be  protracted  ;  the  flash  of  an  electric 
spark  is  sufficient.  But,  what  is  very  remarkable  in  this 
case,  the  rays  which  excite  the  phosphorescence  can  not 
pass  through  a  piece  of  colorless  glass  ;  to  them  it  is  quite^ 
opaque.  The  experiments  of  Mr.  Wilson  show  that  a 
great  number  of  bodies  not  commonly  supposed  to  be 
phosphorescent  are  so*in  reality  ;  that  for  a  few  moments 
after  they  have  been  exposed  to  the  sun,  they  emit  a  phos- 
phorescent light.  Thus,  a  sheet  of  writing  paper,  on  which 
a  key  had  been  laid,  having  been  exposed  for  a  few  mo- 
ments to  the  sun,  on  being  suddenly  removed  to  a  dark 
room  emitted  a  pale  light,  the  shadow  of  the  key  being 
perfectly  visible.  Even  the  hand,  after  being  dipped  in 
the  sunshine,  emitted  subsequently  light  enough  to  be 
visible  in  a  dark  place. 

The  various  principles  of  which  we  have  been  speak- 
in.g  exert  no  ordinary  control  over  the  phenomena  of  the 
natural  world.  Thus  it  is  to  the  influence  of  light  that 
the  vegetable  world  owes  its  existence ;  for  plants  can 
only  obtain  carbon  from  the  air  while  the  sun  is  shining 
on  them,  and  it  is  of  that  carbon  that  their  solid  structures 
are  chiefly  formed.  It  has  been  a  question  to  which  prin- 
ciple this  effect  is  due";  but,  in  1843,  I  proved  that  it  is 
the  yellow  light  which  is  involved.  Dr.  Priestley  discov- 
ered that  the  leaves  of  plants  will  effect  the  decomposi- 
tion of  carbonic  acid  gas  under  water ;  and  on  immersing 
tubes  filled  with  water  holding  this  gas  in  solution,  and 
containing  a  few  green  leaves,  I  found  that  at  the  blue 
extremity  of  the  spectrum  no  effect  whatever  took  place, 
while  decomposition  went  on  rapidly  in  the  yellow  ray. 
It  is  light,  in  contradistinction  to  other  principles,  which  is 
the  agent  producing  this  result,  and  of  its  colored  modifi- 
cations the  yellow  ray  is  the  most  active. 

As  connected  with  the  minute  changes  of  surface  which 
are  effected  when  the  different  radiant  principles  fall  upon 
bodies,  as  in  the  instance  of  the  Daguerreotype,  we  may 
here  allude  to  the  formation  of  spectral  impressions,  which, 
though  invisible,  may  be  brought  out  by  proper  processes. 

What  is  the  relation  of  light  to  the  vegetable  world  ?  "What  color  forms 
the  active  ray  ?  What  was  Dr.  Priestley's  discover}'  ?  What  is  meant 
by  spectral  impressions  ? 


ELECTRICITY.  97 

One  of  these  I  described  several  years  ago.  Take  a  piece 
of  polished  metal,  glass,  or  japanned  tin,  the  temperature 
of  which  is  low,  and  having  laid  upon  it  a  wafer,  coin,  or 
any  other  such  object,  breathe  upon  the  surface  ;  allow 
the  breath  entirely  to  disappear  ;  then  toss  the  object  oft' 
the  surface  and  examine  it  minutely  ;  no  trace  of  any 
thing  is  visible,  yet  a  spectral  impression  exists  on  that 
surface,  which  may  be  evoked  by  breathing  upon  it.  A 
form  resembling  the  object  at  once  appears,  and,  what  is 
very  remarkable,  it  may  be  called  forth  many  times  in 
succession,  and  even  at  the  end  of  many  months.  Other 
instances  of  the  kind  have  subsequently  been  described 
by  M.  Moser. 


LECTURE  XXIV. 

ELECTRICITY.  —  First  Observations  in  Electricity.  —  De- 
scription of  Electrical  Machines.  —  TJic  Spark  a  Test  of 
Electrical  Excitement.  —  Repulsion  of  Electrified  Bodies. 
—  Simple  Means  of  Excitement.  —  Conductors  and  Non- 
conductors .—  Insulation.  —  Electric  Effects  take  place 
through  Glass.  —  Medicated  Tubes. 

IT  was  observed,  six  hundred  years  before  Christ,  that 
a  piece  of  amber,  when  rubbed,  acquired  the  quality  of 
attracting  light  bodies.  This  fact  remained  without  value 
for  more  than  two  thousand  years,  a  striking  memorial  of 
the  barren  nature  of  the  philosophy  of  those  times.  With- 
in the  last  two  hundred  years  it  has  given  birth  to  an  en- 
tire group  of  sciences,  and  established  the  existence  of  a 
great  imponderable  principle,  which,  from  the  Greek 
word  7/Ae/crpov,  signifying  amber,  has  taken  the  name 
ELECTRICITY. 

The  catalogue  of  substances  in  which  electric  develop- 
ment can  be  produced  was  greatly  increased  by  Gilbert, 
who  showed  that  glass,  resin,  wax,  and  many  other  bodies, 
are  equally  effective  as  amber.  To  his  successors  we  owe 
the  electrical  machine,  an  instrument  which  enables  us 
readily  to  demonstrate  the  properties  of  electricity. 


Give  an  example.    What  was  the  first  obsei-vation  made  in  electricity  ? 
From  what  does  the  agent  derive  its  name  ? 


98 


ELECTRICAL    MACHINES. 


fig.  71,  Electrical  machines  are  of  dif- 

ferent kinds.  They  may,  how- 
ever, be  divided  into  plate  and 
cylinder  machines.  These  instru- 
ments are  respectively  represent- 
ed in  Fig.  71  and  Fig.  72.  In 
each  of  them  there  are  three  dis- 
tinct portions.  First,  a  piece  of 
glass,  the  shape  of  which  differs 
in  different  cases  ;  in  Fig.  71  it 
is  a  circular  plate,  in  Fig.  72  a 
cylinder ;  and  from  these  the  in- 
struments take  their  name.  Sec- 
ond, the  rubbers,  made  of  silk  or  leather,  stuffed  with 

hair  :  the  office  of  these  is 
to  press  lightly  on  the  glass 
as  it  turns  round,  and  pro- 
duce friction.  Third,  a 
brass  body,  of  a  cylindri- 
cal or  rounded  shape,  but 
with  points  on  that  portion 
of  it  which  looks  toward 
the  glass.  It  is  support- 
ed on  glass  props,  and  is 
termed  the  prime  conduct- 
or. Some  mechanism,  such  as  a  winch,  is  required  to 
turn  the  glass  on  its  axis ;  and  when  it  is  desired  to  bring 
the  machine  into  activity,  all  the  parts  of  it  having  been 
made  thoroughly  clean  and  dry  by  rubbing  with  a  piece 
of  warm  silk  or  flannel,  a  little  Mosaic  gold  or  amalgam 
of  zinc  being  spread  on  the  rubber,  as  soon  as  the  winch 
is  turned  the  instrument  becomes  excited. 

One  of  the  most  striking  manifestations  of  electrical 
development  is  the  spark ;  this,  which  must  have  been 
often  seen  when  the  back  of  the  domestic  cat  is  rubbed  on 
a  frosty  night,  was  first  discovered  in  the  case  of  glass  or 
sulphur,  by  Otto  Guericke,  and  by  him  referred  to  its 
proper  source,  electric  excitement.  On  presenting  a  brass 
ball  or  the  finger  to  the  prime  conductor  of  the  machine, 
the  spark  passes,  attended  with  a  slight  report.  It  may  be 

'What  varieties  of  electrical  machines  have  we  ?  What  are  the  three 
essential  parts  of  these  machines  ?  What  is  the  rubber  ?  What  is  the 
prime  conductor?  How  is  the  machine  excited? 


ELECTRICAL   LIGHT   AND   REPULSION.  99 

very  beautifully  shown  by  pasting  Fis-  73- 

small  pieces  of  tin  foil  round  a  glass 


tube  in  a  spiral  form,  as  shown  in    a  b  c 

Fig.  73,  a  b  c,  distances  of  the  twentieth  of  an  inch  inter- 
vening between  each  piece,  and  the  ends  of  the  tube  ter- 
minated by  balls.  On  presenting  one  of  these  balls  to  the 
prime  conductor,  and  holding  the  other  in  the  hand,  as 
the  spark  passes,  it  has  to  leap  over  each  interstice  be- 
tween the  spangles  of  tin  foil,  and  exhibits  a  beautiful 
spiral  line  of  light. 

By  pasting  the  tin  foil  011  a  pane  of  glass  in  such  a 
way  as  to  direct  the  spark  F  74 

properly,  words  may  be  written 
in  electric  light,  as  shown  in 
Fig.  74, 

As  the  electric  spark  can 
scarcely  be  confounded  with  any  other  physical  phenom- 
enon whatever,  its  presence  is  always  indubitable  evi- 
dence of  electric  excitement.  Thus,  we  can  prove  that 
electricity  may  be  transferred  to  the  human  body  from 
the  machine,  by  placing  a  man  on  a  Fig.  75. 

stool  supported  by  glass  pillars,  Fig. 
75.    If  he  touches  the  prime  conductor 
with  one  hand,  sparks  may  be  drawn 
from  any  part  of  his  clothing  or  body. 
To  Otto  Guericke,  who  was  also  the 
inventor  of  the  air  pump,  we  owe  another  of  the  most  im- 
portant discoveries  in  electricity  :  that  bodies       pig.16. 
which  have  touched  an  excited  substance  are 
subsequently  repelled  by  it  ;  thus,  if  we  rub 
a  glass  tube,  Fig.  76,  a,  until  it  becomes  elec- 
trified, and  then  present  it  to  a  feather,  b, 
Fig  77        suspended  by  a  silk  thread  to  a 
stand,  c,  the  feather  is  at  first  at- 
tracted, and  then  immediately  re- 
pelled. 

V  On  this  principle,  that  under  certain  circum- 
stances  repulsion  takes  place,  are  founded  dif- 
ferent methods  for  ascertaining  the  existence 

How  may  the  electric  spark  be  exhibited  ?  Why  may  it  be  used  as  a 
test  for  electric  excitement?  Can  electricity  be  transferred  from  the 
machine  to  the  body  ?  What  discovery  did  Otto  Guericke  make  in  elec. 
tricity  ?  How  may  this  property  of  repulsion  be  illustrated  ? 


100  CONDUCTORS    AND    NON-CONDUCTORS. 

of  electric  excitement,  when  too  feeble  to  cause  a  spark. 
Thus,  two  light  balls  of  cork,  Fig.  77  (p.  99),  a  b,  sus- 
pended by  linen  threads  so  as  to  hang  side  by  side,  as 
soon  as  they  are  electrified  repel  each  other. 

It  does  not,  however,  require  an  electrical  machine  to 
demonstrate  the  principles  of  this  agent.  A  piece  of  stout 
brown  paper  three  inches  wide,  and  a  foot  long,  if  held 
before  the  fire  until  it  is  quite  dry  and  smokes,  and  then 
drawn  between  the  knee  and  the  sleeve,  becomes  highly 
excited,  especially  if  the  person  wears  woollen  clothing. 
It  will  yield  sparks  more  than  an  inch  long. 

Let  a,  Fig.  78,  be  the  termination  of  the  prime  conduct- 
Fig-.  78.  or,  and  in  a  hole  in  it  place  the  long 
brass  rod  b,  terminated  by  the  brass 
ball  c.  If  the  finger  is  approached  to 
the  ball,  sparks  freely  pass,  showing  that  along  brass  elec- 
tricity is  conducted  ;  but  if  a  glass  rod  of  the  same  diam- 
eter and  length,  and  terminated  by  a  brass  ball,  be  em- 
ployed, not  a  solitary  spark  can  be  obtained,  proving  that 
glass  is  a  non-conductor  of  electricity. 

The  important  fact  that  substances  may  be  divided  into 
two  classes,  conductors  and  non-conductors,  was  first  ac- 
cidentally discovered  by  Dr.  Grey,  who  found  that  all 
metals  and  moist  bodies  are  conductors,  and  that  glass, 
resins,  wax,  sulphur,  atmospheric  air,  are  non-conductors. 
In  the  treatises  on  chemistry,  tables  may  be  found  exhibit- 
ing the  relations  of  bodies  in  this  respect.  The  conduct- 
ing power  of  the  same  substance  differs  with  circumstan- 
ces ;  thus,  ice  and  glass  are.non-conductors,  but  water  and 
melted  glass  are  conductors. 

We  see,  from  these  facts,  the  explanation  of  the  struc- 
ture of  the  prime  conductor ;  the  electricity  derived  from 
the  glass  by  friction  passes  easily  along  the  brass  portion, 
but  can  not  escape  into  the  earth,  owing  to  the  glass  sup- 
ports, which  refuse  it  a  passage.  When  a  body  is  thus 
placed  upon  glass,  it  is  said  to  be  electrically  insulated, 
and  the  process  is  called  insulation. 

Although  electricity  can  not  pass  through  glass,  Sir 
Isaac  Newton  found  that  this  substance  is  no  impediment 

By  what  simple  means  may  electrical  experiments  be  made  ?  How 
may  it  be  proved  that  brass  is  a  conductor  and  glass  a.  non-conductor  ? 
Mention  some  of  the  leading  substances  belonging  to  each  of  these  classes. 
Explain  the  structure  of  the  prime  conductor.  Can  electric  influences 
pass  through  glass  ? 


TWO    SPECIES   OF 

to  the  exertion  of  its  influences.  .  Thus, 
in  Fig.  79,  if  a  be  the  brass  ball  ©f  the 
prime  conductor,  any  light  objects,  such 
as  bits  of  paper  or  fragments  of  cork, 
placed  on  a  metal  stand,  b,  beneath  will 
be  attracted  ;  and  though  a  pane  of 
glass,  c,  be  placed  between  a  and  b,  still 
the  same  phenomenon  takes  place. 

Soon  after  electricity  became  a  subject  of  popular  at- 
tention, it  was  currently  believed,  that  if  medicines  of  va- 
rious kinds  were  sealed  up  in  glass  tubes,  and  the  tubes 
electrically  excited,  their  peculiar  virtues  would  be  exhal- 
ed in  such  a  manner  as  to  impress  the  operator  with  their 
specific  purgative,  emetic,  or  other  powers.  Like  many 
of  the  popular  delusions  of  our  times,  this  imposture  was 
supported  by  the  most  cogent  evidence,  and  maladies  cur- 
ed publicly  all  over  Europe.  Like  them,  these  "  medica- 
ted tubes"  have  served  to  prove  the  worthlessness  of  hu- 
man testimony  when  derived  from  the  prejudiced  and 
ignorant. 


LECTURE  XXV. 

THEORY  OF  ELECTRICAL  INDUCTION. — Two  Species  of 
Electricity. —  Their  Names. — General  Law  of  Attraction 
and  Repulsion. —  Theory  of  Induction. — Permanent  Ex- 
citement by  Induction. —  Takes  place  through  Glass. — 
Illustrative  Experiments. 

A  VERY  celebrated  French  electrician,  Dufay,  having 
caused  a  light,  downy  feather  to  be  repelled  by  an  excit- 
ed glass  tube,  intended  to  amuse  himself  by  chasing  it 
round  the  room  with  a  piece  of  excited  sealing-wax.  To 
his  surprise,  instead  of  being  repelled,  the  feather  was  at 
once  attracted.  On  examining  the  cause  of  this  more  mi- 
nutely, he  arrived  at  the  conclusion  that  there  are  two 
species  of  electricity,  the  one  originating  when  glass  is 
excited,  and  the  other  from  resin  or  wax.  To  these  he 
gave  the  names  of  vitreous  and  resinous  electricity,  thus 

What  was  formerly  meant  by  medicated  tabes  1  How  was  it  first  dis- 
covered that  there  are  two  species  of  electricity  1  What  names  have 
been  given  to  these  electricities  1 

I  2 


INDUCTION. 


.pgiptmg;  put  tljeir  origin  ;,  they  are  also  called,  for  reasons 
\\vh5tjfc  J"p3V  be  giy  en?  b&ce  after,  positive  and  negative  elec- 
tricities'. ' 

He  found  that  these  different  electricities  possess  the 
same  general  physical  qualities  ;  they  are  self-repulsive, 
but  the  one  is  attractive  of  the  other.  This  is  readily 
proved  by  hanging  a  feather  by  a  linen  thread  to  the  prime 
conductor  of  the  machine,  and,  when  it  is  excited,  bringing 
near  to  it  an  excited  glass  tube.  The  feather  is  already 
vitreously  electrified,  and  the  tube,  being  in  the  same  con- 
dition, at  once  repels  it  ;  but  a  stick  of  excited  sealing- 
wax  being  resinously  electrified,  that  is  to  say,  in  the 
opposite  condition  to  the  feather,  at  once  attracts  it. 
Two  cork  balls,  as  in  Fig.  77,  suspended  by  conducting 
threads,  always  repel  one  another  when  both  are  excited 
either  vitreously  or  resinously  ;  but  if  one  be  vitreous  arid 
the  other  resinous,  they  attract. 

These  various  results  may  all  be  grouped  under  the 
following  general  law,  which  includes  the  explanation  of  a 
great  many  electrical  phenomena.  Bodies  electrified  dis- 
similarly attract,  and  bodies  electrified  similarly  repel  ;  or, 
more  briefly,  like  electricities  repel,  and  unlike  ones  attract. 
There  are  many  ways  in  which  electrical  excitement 
can  be  developed  :  in  the  common  machine  it  is  by  fric- 
tion ;  in  the  tourmaline,  a  crystallized  gem,  by  heat  ;  and  in 
other  cases  by  chemical  action  and  by  conduction.  Elec- 
trical disturbance  also  very  often  arises  from  induction. 

By  the  term  electrical  induction  we  mean  that  a  body 
which  is  already  excited  tends  to  disturb  the  condition  of 
others  in  its  neighborhood,  inducing  in  them  an  electric 
condition. 

Thus,  let  a,  Fig.  80,  be  the  terminal  ball  of  the  prime 
Fig.  80.  conductor,  and  a  few  inches 

£\  fK    off  let  there  be  placed  a  seo 

ct   °*\l  _  d       ondary  conductor,  b  c,  of  brass 
D     supported  on  a  glass  stand,  and 
at  each  extremity,  b  and  c,  of 
the  conductor,  let  there  be  ar- 
ranged   a  pair  of  cork  balls 


I 


What  are  their  physical  qualities  ?  How  may  this  self-repulsion  and 
toutual  attraction  be  proved  ?  "What  is  the  general  law  of  electric  attrac- 
tions and  repulsions  ?  In  what  ways  may  electric  excitements  be  devel- 
oped ?  What  is  the  meaning  of  electric  induction  ?  Give  an  illustration. 


ELECTRICAL    INDUCTION.  103 

suspended  by  linen  threads,  as  shown  in  the  figure.  As 
soon  as  the  ball,  a,  is  electrified  by  turning  the  machine, 
and  without  any  spark  passing  from  it  to  the  secondary 
conductor,  the  balls  will  begin  to  diverge,  showing  that 
the  condition  of  that  conductor  is  disturbed  by  the  neigh- 
borhood of  the  excited  ball,  a. 

It  will  farther  be  found,  on  presenting  an  excited  piece 
of  sealing  wax  to  the  pairs  of  cork  balls,  that  one  set  is 
attracted,  and  the  other  repelled.  They  are,  therefore,  in 
opposite  electrical  states.  The  disturbing  ball  is  vitre- 
ously  electrified,  and  that  end  of  the  secondary  conductor 
nearest  it  is  resinous,  the  farther  end  being  vitreous.  If 
the  disturbing  ball,  #,  be  now  removed,  the  electric  dis- 
turbance ceases,  and  the  corks  no  longer  diverge. 

These  phenomena  of  electric  induction  are  not  depend- 
ent on  the  shape  of  bodies.  Let  there  be 
two  flat  circular  plates,  a  b,  Fig.  81,  sup- 
ported on  glass  stands,  and  set  a  few  inches 
apart,  looking  face  to  face.  Let  one  of  them, 
«,  be  electrified  positively  by  contact  with 
the  prime  conductor,  as  indicated  by  the 
sign  + ;  it  immediately  induces  a  change 
in  the  opposite  plate,  the  nearest  face  of 
which  becomes  negative  — ,  and  the  more  distant,  positive. 
It  is  evident  that  this  disturbance  is  a  consequence  of  the 
law,  that  "like  electricities  repel,  and  unlike  ones  attract." 
In  the  plate  &,  both  species  of  electricity  exist,  and  a  be- 
ing made  positive,  even  though  at  a  distance,  exerts  its 
attractive  and  repulsive  agencies  on  the  electric  fluid  of 
b,  the  negative  electricity  of  which  it  attracts,  and  draws 
near  to  it ;  the  positive  it  repels  and  drives  to  the  farthest 
side  ;  so  that  the  disturbed  condition  of  the  body  b  is  a 
result  of  the  fact,  that  a  being  electrified  positively,  will 
repel  positive  electricity  and  attract  negative. 

Now  let  the  plate  b  be  touched  by  the  finger,  or  a 
channel  of  communication  opened  with  the  earth;  the 
positive  electricity  of  a  still  exerting  its  repulsive  agency 
on  that  of  b,  will  drive  it  into  the  ground,  and  b  will  now 
become  negative  all  over. 

Lot  b  be  once  more  insulated,  by  breaking  its  commu- 

In  a  secondary  conductor  disturbed  by  an  electrified  body,  what  are  the 
conditions  of  its  ends  ?  What  is  the  cause  of  this  disturbance  ?  How- 
may  wo  by  induction  permanently  electrify  a  body  ? 


104  MISCELLANEOUS    EXPERIMENTS. 

nication  with  the  ground,  and  let  a  be  removed;  A  \v\i\ 
now  be  found  that  b  is  permanently  electrified,  and  in  the 
Dpposite  condition  to  a. 

By  manipulating  in  this  manner,  we  can,  therefore,  ef- 
Fig.  82.      feet  a  permanent  disturbance  in  the  condition 
of  an  insulated  body,  by  bringing  an  excited  one 
in  its  neighborhood. 

In  these  changes,  the  intervention  of  a  piece 
of  glass  makes  no  difference.  Let  a  circulai 
plate  of  glass,  a,  Fig.  82,  be  set  so  as  to  inter 
vene  between  the  metallic  plates,  a  and  b,  and 
still  all  the  phenomena  occur  as  before.  Elec 
trie  induction,  therefore,  can  take  place  through  glass. 
Fig  83  ®n  ^G  principles  of  induction,  and  of  electric 
attraction  and  repulsion,  many  very  interesting 
experiments  may  be  explained.  The  following 
may  serve  as  examples  :  To  the  ball  of  the  prime 
conductor,  Fig.  83,  let  there  be  suspended  a  cir- 
cular plate  of  "brass,  a,  six  inches  in  diameter, 
horizontally,  and  beneath  it  another  plate,  b, 
supported  on  a  conducting  foot,  parallel  and  at  a 
distance  of  three  "or  four  inches.  On  the  lower 
plate,  b,  place  slips  of  paper  or  of  other  light 
substance,  cut  into  the  figure  of  men  or  animals.  On  set- 
ting the  machine  in  motion,  so  as  to  electrify  the  upper 
plate,  the  objects  move  up  and  down  with  a  dancing  mo- 
tion ;  and  the  cause  is  obvious :  the  plate  a  being  posi- 
tive, repels  by  induction  the  positive  electricity  of  the 
figures  through  the  conducting  stand  into  the  earth,  and 
thus,  they  being  rendered  negative,  are  attracted  by  the 
upper  plate  ;  on  touching  it,  they  become  electrified  posi- 
tively like  it,  and  then  are  repelled,  and  fall  down  to  dis- 
Fi  84  charge  their  electricity  into  the  ground, 

and  this  motion  is  continually  repeated. 
Upon  a  horizontal  brass  bar,  a  b,  Fig. 


m84,  three  bells  are  suspended,  the  outer 
ones  at  a  and  b  by  chains,  the  middle 
I       «     1  one  at  c  by  a  silk  thread.     Between  the 
^^KwwwKoeaj  bells,  the  metallic  clappers,  d  e,  are  sus- 
*^  pended  by  silk,  and  from  the  center  bell 

Can  electrical  induction  take  place  through  glass  ?  Describe  the  ex- 
periment of  the  dancing  figures,  and  explain  the  principles  involved  in  it. 
Describe  the  experiment  of  the  bells,  and  the  cause  of  their  ringing. 


MISCELLANEOUS    EXPERIMENTS. 


105 


Fig.  85. 


the  chain  f  extends  to  the  table.  On  hanging  the  ar- 
rangement by  the  hook  at  g  to  the  prime  conductor,  the 
bells  ring  ;  the  clappers  moving  from  the  outer  to  the  cen- 
tral bell  and  back,  alternately  striking  them. 

On  a  pivot,  a,  Fig.  85,  suspend  a  bell  jar  having  four 
pieces  of  tin  foil  pasted  on  its 
sides,  b  c  d;  connect  the  jar,  by 
means  of  the  insulated  wire  y,  with 
the  prime  conductor,  so  that  the 
pieces  of  tin  foil  may  receive 
sparks.  On  the  opposite  side  ar- 
range a  conductor,  #,  in  connection 
with  the  ground  by  a  chain.  On 
putting  the  machine  into  activity, 
the  jar  will  commence  rotating  on  its  pivot. 

Take  a  cake  of  sealing  wax  or  gum  lac,  eight  or  ten 
inches  in  diameter,  and  receive  on  its  surface  a  few  sparks 
from  the  prime  conductor  by  bringing  it  near  the  ball. 
Then  blow  upon  its  surface  from  a  small  pair  of  bellows, 
a  mixture  of  flowers  of  sulphur  and  red-lead,  which  have 
been  intimately  ground  together  in  a  moitar.  This  mix- 
ture is  of  an  orange  color,  but  the  moment  it  impinges  on 
the  cake  it  is,  as  it  were,  decomposed ;  the  yellow  sulphui 
settling  on  one  portion,  and  the  red-led  on  another,  giv 
ing  rise  to  very  curious  and  fantastical  figures. 


LECTURE  XXVI. 

LAWS  OP  THE  DISTRIBUTION  OF  ELECTRICITY,  AND  THE 
GENERAL  THEORIES. — Distribution  of  Electricity. —  On 
a  Sphere. — Ellipsoid. — Action  of  Points. — Franklin's 
Discovery  of  the  Identity  of  Electricity  and  Lightning 
—  The  Leyden  Jar. —  The  discharging  Rod. —  The  Elec  • 
trie  Battery. 

WHEN  electricity  is  communicated  to  a  conducting  body, 
it  does  not  distribute  itself  uniformly  through  the  whole 
mass,  but  exclusively  upon  the  surface ;  thus,  if  to  the 


Explain  the  arrangement  and  cause  of  movement  of  the  rotatory  jar. 
How  may  powder  of  sulphur  and  red-lead  mixed  together  be  separated  ? 
Does  electricity  distribute  itself  on  the  surface  or  in  the  interior  of  bodies  ? 


106  DISTRIBUTION    OF    ELECTRICITY". 

spherical  ball  a,  Fig.  86,  supported 
on  an  insulating  foot,  b,   there  be 
adjusted    two    hemispherical    caps, 
c  c,    also   on    insulating  handles,  it 
may  be  proved  that  any  electricity 
communicated  to  a  distributes  itself 
entirely  on  its  surface ;    for  if  we 
place  upon  a  the  caps  e  c,  and  then  remove  them,  it  will  be 
found  that  every  trace  of  electricity  has  disappeared  from 
a,  and  has  accumulated  on  the  caps,  which,  while  they 
were  upon  the  ball,  formed  its  superficies. 
Fi    87         Again,  if  we  take  a  large  brass  ball,  <z,  Fig.  87, 
r          supported  on  an  insulating  stand,  and  having  on 
its  upper  portion  an  aperture,  b,  through  which 
we  may  have  access  to  its  interior,  it  will  be  found, 
on  examination,  that  the  most  delicate  electrom- 
eters can  discover  no  electricity  within  the  ball, 
the  whole  of  it  being  on  the  external  superficies. 
In  the  case  of  a  spherical  body,  not  only  is  the 
distribution  entirely  superficial,  but  it  is  also  uni- 
form ;  each  portion  of  the  sphere  is  electrified  alike.     But 
where,  instead  of  a  spherical,  we  have  an  ellipsoidal  body, 
it  is  different  j  thus,  if  we  examine  the  condition  of  such 
Fig.  88.  a  conductor,  Figure  88,  the  quantity 

of  electricity  in  its  middle  portion, 
as  at  a,  will  be  the  smallest,  and 
it  increases  as  we  advance  toward 
the  ends,  b  and  c;  and  in  different 
ellipsoids,  as  the  length  becomes 
greater,-  so  the  amount  of  electricity 
found  on  the  extremities  is  greater. 
When,  therefore,  a  conductor  of  an 
oblong  spheroidal  shape  is  used,  the  intensity  of  the  elec- 
tricity at  the  extremities  of  the  two  axes,  a  d  and  b  c,  Fig. 
88,  is  exactly  in  the  proportion  of  the  length  of  those  axes 
themselves  ;  and  should  the  disproportion  in  length  and 
breadth  of  the  conducting  body  be  very  great,  as  in  the 
case  of  a  long  wire  or  other  pointed  body,  a  very  great 
concentration  will  take  place  upon  the  points.  On  this 

How  may  its  superficial  distribution  be  proved  ?  In  the  interior  of  an 
electrified  hollow  ball,  does  any  electricity  exist  ?  On  a  spherical  body 
is  the  distribution  unifonn  ?  How  is  it  on  an  ellipsoid  ?  When  the  dis- 
proportion of  the  axes  of  the  ellipsoid  is  great,  what  is  the  distribution  ? 


IDENTITY    OF    LIGHTNING    AND    ELECTRICITY.       107 

principle  we  explain  the  effect  of  pointed  bodies  on  con- 
ductors :  if  the  prime  conductor  of  the  machine  have  a 
needle  or  pin  fixed  upon  it,  the  electricity  escapes  away 
into  the  air,  visibly  in  a  dark  room  ;  and  in  the  same  way, 
if  pointed  bodies  surround  the  electrical  machine,  it  can 
not  be  highly  excited,  as  they  rapidly  take  the  charge  from 
its  conductor. 

At  a  very  early  period  electricians  had  observed  the 
close  similarity  between  the  phenomena  of  the  electric 
spark  and  those  of  lightning,  but  in  the  year  1752  Dr. 
Franklin  proved  that  they  were  identical.  He  was  waiting 
for  the  erection  of  the  spire  of  a  church  in  Philadelphia,  on 
the  extremity  of  which  he  intended  to  raise  a  pointed  metal 
rod,  with  a  view  of  withdrawing  the  electricity  from  the 
clouds,  when  the  accidental  sight  of  a  boy's  kite  suggested 
to  him  that  ready  means  of  obtaining  access  to  the  more 
elevated  regions  of  the  air.  Accordingly,  having  stretched 
a  silk  handkerchief  over  a  light  wooden  cross,  and  ar- 
ranged it  as  a  kite,  he  attached  to  it  a  hempen  string  ter- 
minating in  a  silk  cOrd,  and,  taking  advantage  of  a  thunder 
storm,  raised  it  in  the  air;  for  a  time  no  result  was  ob- 
tained, but  the  string  becoming  wet  by  the  rain,  and  there- 
by rendered  a  better  conductor,  he  perceived  the  filaments 
which  hung  upon  it  repelling  one  another,  and  on  present- 
ing his  knuckle  to  a  key  which  had  been  tied  to  the  end 
of  the  hempen  string,  received  an  electric  spark.  The 
identity  of  lightning  and  electricity  was  proved. 

Franklin  soon  made  a  useful  application  of  his  discov- 
ery ;  he  proposed  to  protect  buildings  from  the  effects  of 
lightning  by  furnishing  them  with  a  metallic  rod,  pointed 
at  its  upper  extremity  and  projecting  some  feet  above  the 
highest  part  of  the  building,  and  continuously  extending 
downward  until  it  was  deeply  buried  in  the  ground.  This 
contrivance,  the  lightning  rod,  is  now,  as  is  well  known, 
extensively  applied. 

There  are  two  theories  respecting  the  nature  of  elec- 
tricity :  1st,  Franklin's  theory,  which  assumes  that  there 
is  but  one  fluid ;  2d,  the  theory  of  two  fluids,  called  also 
Dufay's  theory. 

How  may  we  explain  the  effect  of  pointed  bodies  ?  Under  what  cir- 
cumstances was  the  discovery  of  the  identity  of  lightning  and  electricity 
made  ?  "What  is  the  lightning  rod  ?  What  theories  of  electricity  have 
been  introduced  ? 


108  THEORIES    OF    ELECTRICITY. 

Franklin's  theory  is,  that  there  exists  throughout  all 
space  a  subtle  and  exceedingly  elastic  fluid,  called  the 
electric  fluid,  the  peculiarity  of  which  is,  that  it  is  repuls- 
ive of  its  own  particles,  but  attractive  of  the  particles  of 
other  matter ;  that  there  is  a  specific  quantity  of  this 
fluid  which  bodies  are  disposed  to  assume  when  in  a  nat- 
ural condition  or  state  of  equilibrium ;  and  that,  if  we  com- 
municate to  them  more  than  their  natural  quantity,  they 
become  positively  electrified;  or,  if  we  take  from  a  portion 
of  that  which  is  natural  to  them,  they  become  negatively 
electrified. 

Dufay's  theory  is,  that  there  exists  throughout  all  space 
a  universal  medium,  called  the  electric  fluid,  of  which 
the  immediate  properties  are  unknown,  but  which  is  com- 
posed of  two  species  or  varieties  of  electricity,  the  vitreous 
and  resinous,  called  also  the  positive  and  negative ;  that, 
as  respects  itself,  each  of  these  electricities  is  repulsive, 
but  attractive  of  the  other  kind ;  and  that,  when  they  co- 
exist in  equal  quantities  in  a  body,  it  is  in  a  neutral  state 
or  condition  of  equilibrium,  but  if  the  positive  or  negative 
electricities  are  in  excess,  it  is  accordingly  positively  or 
negatively  electrified. 

In  some  respects  the  theory  of  two  electricities  has  ad- 
vantages over  that  of  one;  by  it  several  phenomena  can  be 
explained  which  are  difficult  of  explanation  by  the  other. 
Among  such  may  be  mentioned  the  repulsion  of  negatively 
electrified  bodies,  and  the  distribution  of  negative  elec- 
tricity on  the  surface  of  conductors,  which  is  the  same  as 
that  of  positive. 

On  the  principles  of  either  of  these  theories  we  can 
see  how  it  is  that  we  can  never  produce  one  kind  of  elec- 
tricity without  the  other  simultaneously  appearing.  In 
the  common  electrical  machine,  if  the  revolving  glass  is 
positively  electrified,  the  rubbers  which  produce  the  fric- 
tion are  negative  ;  in  the  tourmaline,  if  one  end  of  the 
crystal,  when  warmed,  becomes  positive,  the  other  end  is 
negative.  The  two  varieties  must  be  always  co-ordinately 
generated. 

In  1745  the  Leyden  jar  was  discovered.  This  consists 
of  a  glass  jar,  Fig.  89,  coated  on  its  inside  with  a  piece 

What  is  Franklin's  theory?  "What  is  the  theory  of  Dufay?  In  what 
points  does  the  latter  appear  to  be  more  correct  than  the  former?  Why 
are  both  electricities  always  produced  together  ? 


THE    LEYDEN    JAR. 


109 


of  tin  foil  within  an  inch  or  two  of  its  upper  Fis-  89- 
edge,  and  also  on  its  outside  to  the  same  point ; 
through  the  cork  which  closes  the  mouth  of 
the  jar,  a  brass  rod,  terminated  by  a  ball, 
passes ;  the  rod  reaches  down  to  the  inside 
coating  and  touches  it.  On  holding  this  in- 
strument by  the  exterior  coating,  and  pre- 
senting its  ball  to  the  prime  conductor,  a  tor- 
rent of  sparks  passes  into  the  jar ;  and  when 
it  is  fully  charged,  if,  still  retaining  one  hand 
in  contact  with  the  outside,  we  touch  the  ball,  a  bright 
spark  passes,  with  a  loud  snapping  noise,  and  the  operator 
receives  through  his  arms  and  breast  what  is  called  the 
electric  shock. 

If  we  take  the  discharging  rod,  Fig.  90,  consisting  Fig  90 
of  two  brass  arms,  a  a,  terminated  by  balls  working 
on  a  joint,  b,  and  supported  by  an  insulating  handle, 
c,  by  bringing  one  of  its  balls  in  contact  with  the 
outside  coating  of  a  Leyden  jar,  and  its  other  ball 
with  the  ball  of  the  jar,  the  discharge  will  take  place 
as  before,  but  the  operator,  protected  by  the  glass 
handle,  receives  no  shock. 

If  between  the  outside  coating  of  ajar  and  one  of 
the  balls  of  the  discharging  rod,  a  piece  of  card- 
board is  made  to  intervene,  arid  the  spark  passed, 
the  card  will  be  found  to  be  perforated,  a  burr  being  raised 
on  both  sides  of  it,  as  though  two  threads  had  been  drawn 
through  the  hole  in  opposite  di-  Fig.  91. 

rections  at  the  same  time;  and 
from  this  an  argument  in  favor 
of  the  theory  of  two  fluids  has 
been  drawn. 

When  a  great  number  of  jars 
are  connected  together,  so  that 
all  their  inside  coatings  unite, 
and  all  their  outside  coatings  are 
also  in  contact,  they  constitute 
what  is  termed  an  electric  bat- 
tery, as  seen  in  Fig.  91.  By  this 

Describe  the  structure  of  the  Leyden  jar.  How  may  it  be  used  ? 
Describe  the  discharging  rod.  How  is  it  used  ?  What  is  the  effect  when 
the  discharge  is  passed  through  a  piece  of  card-board  ?  Describe  the  elec 
trie  battery. 

K 


110  CONDENSING    ACTION. 

instrument  many  of  the  more  violent  effects  of  electricity 
may  be  illustrated,  such  as  the  splitting  of  pieces  of  wood 
and  the  ignition  and  dispersion  of  metallic  wires. 


LECTURE  XXVII. 

ELECTRICAL  INSTRUMENTS  AND  FARADAY'S  THEORY  OF 
ELECTRIC  POLARIZATION.- — Theory  of  the  Ley  den  Jar. 
— Quadrant,  Gold-leaf,  and  Torsion  Electrometers. — 
Theory  of  Electric  Polarization.  —  Specific  Inductive 
Capacity. 

THE  office  which  is  discharged  by  the  metallic  coatings 
Fig.  92.  of  a  Leyden  jar  is  illustrated  by  the  apparatus, 
Fig.  92.  It  consists  of  a  conical  glass  jar,  to 
the  interior  and  exterior  of  which  movable  coat- 
ings of  thick  tin  plate  are  adapted,  the  interior 
one  having  a  rod  and  ball  projecting  from  it. 
This  may  be  charged  like  any  other  Leyden  vial, 
but  on  taking  off  its  outside  coating  and  remov- 
ing its  interior,  they  may  be  handled  and 
brought  in  contact  with  each  other,  and  no  spark 
passes  ;  but  on  restoring  them  to  their  former  position, 
and  applying  the  discharging  rod,  the  jar  is  discharged. 
They  therefore  only  serve  to  make  a  complete  conducting 
communication  between  all  parts  on  the  interior  and  all 
on  the  exterior  of  the  jar. 

The  condensing  action  of  the  Leyden  vial,  which  ena- 
bles it  to  hold  so  large  a  quantity  of  electricity,  is  due  to 
induction.  When  the  inner  coating  is  brought  in  contact 
with  the  prime  conductor,  it  participates  in  its  electrical 
condition.  We  may  therefore  suppose  it  to  be  positively 
electrified.  The  positive  electricity  of  the  interior,  de- 
composing the  electric  fluid  of  the  outside  coating,  repels 
its  positive  electricity  into  the  earth  ;  for  to  charge  a  Ley- 
den vial  the  outside  coating  is  placed  in  communication 
with  the  ground.  It  therefore  appears  that  the  inner  coat- 
ing is  positive,  the  outer  negative,  and  the  whole  jar,  view- 

What  is  the  office^of  the  coatings  of  the  Leyden  jar?  How  may  this 
be  proved  ?  To  what  cause  is  the  condensing  action  of  the  Leyden  jar 
due  ?  "What  is  the  action  of  the  positive  electricity  deposited  on  the  inner 
coating,  on  the  electric  fluid  of  the  outer  ? 


ACTION    OF    THE    LEYDEN    JAR.  Ill 

ed  together,  is  in  the  neutral  condition.  The  interior 
coating  continues,  under  these  circumstances,  to  receive  a 
farther  charge  from  the  prime  conductor  by  induction 
through  the  glass  ;  this  again  repels  more  of  the  same 
kind,  th6  positive,  into  the  ground,  and  the  negative  accu- 
mulates as  before.  In  this  manner  an  indefinite  quantity 
might  be  accumulated,  were  it  not  for  the  fact  that,  owing 
to  the  distance  which  intervenes  between  the  two  coatings, 
by  reason  of  the  thickness  of  the  glass,  the  quantity  of 
positive  electricity  in  the  interior  is  never  precisely  neu- 
tralized by  the  quantity  of  negative  on  the  exterior,  for 
all  inductive  actions  enfeeble  as  the  distance  increases. 

The  action  of  the  Leyden  vial  may  be  illustrated  by  the 
following  experiments  :  within  an  Fig.  93. 

inch  of  the  ball,  #,  of  the  prime  con-  _ 
ductor,  Fig.  93>  bring  a  secondary  ~~ 
conductor,  b,  supported  on  an  insu- 
lating stem,  c,  and  on  putting  the 
electrical  machine  in  activity,  two 
or  three  sparks  will  pass  from  a  to 
b,  but  after  that  no  more.  The  cause  of  the  refusal,  on  the 
part  of  the  secondary  conductor,  to  receive  any  farther 
charge  is  obviously  due  to  the  fact  that  the  electricity 
which  is  already  communicated  to  it  repels  that  upon  the 
ball,  a,  and  prevents  the  passage  of  any  more. 

If  now  we  take  a  Leyden  jar,  &,  Fig.  94,  and  having 
insulated  it  on  a  stand,  bring  it  within  a  Figf  94. 

short  distance  of  the  ball,  a,  of  the  prime 
conductor,  it  in  the  same  manner  will 
only  receive  a  few  sparks.  But  if  we 
place  a  conductor,  c,  which  is  connected 
with  the  ground,  near  to  the  outside  coat- 
ing, it  will  be  found  that  for  every  spark 
that  passes  between  a  and  b  one  passes 
between  the  outside  coating  and  c,  and 
the  sparks  follow  each  other  in  rapid  suc- 
cession, until  the  jar  becomes  fully  charged.  From  this, 
therefore,  we  gather,  that  while  positive  electricity  is 

Why  must  the  outer  coating  be  in  connection  with  the  ground  ?  Why  ia 
the  charge  of  the  jar  limited?  What  is  the  reason  that  a  secondary  insu- 
lated conductor  refuses  to  receive  more  than  two  or  three  sparks  ?  When 
the  Leyden  jar  is  insulated,  can  it  be  charged  ?  On  bringing  a  conduct- 
or in  connection  with  the  ground,  near  the  outer  coating,  what  is  the 
result? 


112  ELECTROMETERS. 

passing  into  the  interior  of  the  jar,  it  is  escaping  from  the 
exterior,  and  that  the  reason  the  jar  condenses  is  because 
its  sides  are  in  opposite  conditions,  the  positive  electrici- 
ty of  the  interior  being  nearly  neutralized  by  the  nega- 
tive electricity  of  the  exterior. 

Fig.  95.  Electrometers  are  instruments  for  measuring 
the  intensity  of  electric  excitement.  The  cork 
balls,  which  were  represented  in  Fig.  77,  are  one 
of  the  most  simple  of  these  contrivances.  The 
distance  to  which  they  will  diverge  is  a  rough 
measure  of  the  intensity  of  the  electric  force. 
The  quadrant  electrometer  depends  essentially 
on  the  same  principles.  It  consists  of  an  up- 
right stem  of  wood,  Fig.  95,  to  which  is  affixed 
a  semicircular  piece  of  ivory,  from  the  center 
of  which  there  hangs  a  light  cork  ball  playing 
upon  a  pivot.  When  this  instrument  is  placed  on  the 
prime  conductor  or  other  electrified  body,  the  stem  par- 
ticipates in  the  electricity,  and  repelling  the  cork  ball 
which  hangs  in  contact  with  it,  the  amount  of  repulsion 
may  be  read  off  on  the  graduated  semicircle  ;  but  it  is 
obvious  that  the  number  of  degrees  is  not  expressive  of 
the  true  electrical  intensity,  and  that  no  force,  no  matter 
what  its  intensity  may  be,  can  ever  repel  the  ball  beyond 
ninety  degrees. 

The  gold-leaf  electrometer,  Fig.  96, 
consists  of  a  glass  cylinder,  a,  in  which 
two  gold  leaves  are  suspended  from  a 
conducting  rod  terminated  by  a  ball  or 
plate  b.  On  the  glass  opposite  the  leaves 
pieces  of  tin  foil  are  pasted,  so  that  when 
the  leaves  diverge  fully  they  may  dis- 
charge their  electricity  into  the  ground. 
This  is  a  very  delicate  instrument  for 
discovering  the  presence  of  electricity,  but  the  torsion 
electrometer  of  Coulomb  is  to  be  preferred  when  it  is  re- 
quired to  have  exact  measures  of  the  quantity. 

Coulomb's  electrometer  consists  of  a  glass  cylinder,  a, 
Fig.  97,  upon  the  top  of  which  there  is  fixed  a  tube,  b, 
in  the  axis  of  which  hangs  a  glass  thread,  b  a,  to  the 

Describe  the  cork  b'all  electrometer.  Describe  the  quadrant  electronic  • 
ter.  Why  does  the  quadrant  electrometer  give  inaccurate  indications  ?  De- 
scribe the  gold-leaf  electrometer.  Describe  Coulomb's  torsion  electrometer 


THE    TORSION    ELECTROMETER.  113 

lower  end  of  which  a  small  bar  of  gum  lac,  c,  with  a 
gilt  pith  ball  at  each  extremity,  is  fasten- 
ed. Through  an  aperture  in  the  top  of 
the  glass  cylinder,  another  gum  lac  rod, 
d,  with  gilt  balls,  may  be  introduced. 
This  goes  under  the  name  of  the  carrier 
rod. 

If,  now,  the  lower  ball  of  the  carrier 
rod  be  charged  with  the  electricity  to  be 
measured,  and  introduced  into  the  inte- 
rior of  the  cylinder,  as  seen  in  the  figure, 
it  will  repel  the  movable  ball.  By  taking 
hold  of-the  button  &,  to  which  the  upper 
end  of  the  glass  thread,  a,  is  attached, 
we  may,  by  twisting  the  glass  thread  for- 
cibly, bring  the  carrier  ball  and  the  mova- 
ble ball  in  contact.  The  number  of  degrees  through  which 
the  thread  require-s  to  be  twisted  represents  the  amount  of 
electricity.  To  the  button,  Z>,  an  index  and  scale  are  attach- 
ed, not  shown  in  the  figure.  By  this  we  can  tell  the  num- 
ber of  degrees  of  twist  or  torsion  which  have  been  given 
to  the  thread.  These  angles  of  torsion  are  exactly  pro- 
portional to  the  quantities  of  electricity.- 

Many  of  the  fundamental  phenomena  of  electricity  have 
been  explained  by  Dr.  Faraday  upon  the  hypothesis  that 
induction  is  an  action  of  polarization,  taking  place  in  the 
contiguous  molecules  of  non-conducting  media,  and  prop- 
agated in  curved  lines. 

Whatever  may  be  the  form  or  constitution  of  bodies, 
an  electric  charge  can  not  be  given  to  them  without  at 
the  same  time  giving  a  charge  of  the  opposite  kind,  but 
of  the  same  amount,  to  them  or  other  bodies  in  their  vicini- 
ty. This  charge  is  not  confined  upon  their  surfaces  by 
the  pressure  of  the  atmosphere,  but  through  the  polariza- 
tion of  the  aerial  or  solid  particles  of  the  surrounding 
dielectrics,  producing  in  them  a  charge  of  the  same 
amount,  but  of  an  opposite  kind.  Thus,  if  a  positively 
electrified  ball  be  placed  in  the  center  of  a  hollow  metal- 
lic sphere,  the  intervening  space  being  filled  with  atmos- 
pheric air,  the  charge  is  not  retained  upon  the  ball  by  the 

What  is  the  basis  of  Faraday's  theory  of  induction?  On  this  theory, 
are  charges  confined  by  pressure  of  the  air  ?  Describe  the  action  of  an 
electrified  ball  in  the  interior  of  a  sphere. 

K2 


114 

pressure  of  the  air,  but  because  each  aerial  particle  as- 
sumes by  induction  a  polarity  of  the  opposite  kind  on  the 
side  nearest  to  the  ball,  and  of  the  same  kind  on  the  side 
farthest  off.  This  state  of  force  is  therefore  communica- 
ted to  the  interior  of  the  hollow  sphere,  which  is  electrified 
to  the  same  amount,  but  of  an  opposite  kind  to  the  ball. 
That  this  polarization  of  the  particles  takes  place,  is 
shown  by  the  position  which  small  silk  fibres  or  spangles 
of  gold  assume  when  placed  in  oil  of  turpentine,  through 
which  induction  is  established.  Each  particle  disturbs 
not  merely  that  which  is  before  it  or  behind  it,  but  it  is  in 
an  active  relation  with  all  surrounding  it,  and  hence  the 
polarity  can  be  propagated  in  curved  lines,  and  induction 
take  place  round  corners  and  behind  obstacles. 

On  these  principles,  wre  can  easily  account  for  the  dis- 
tribution of  electricity  on  spherical  or  ellipsoidal  conduct- 
ors, the  repulsion  of  bodies  similarly  electrified,  the  con- 
densing action  of  the  Leyden  vial,  and  many  other  similar 
phenomena. 

By  a  variety  of  experiments,  Dr.  Faraday  has  proved 
that  inductive  action  takes  place  in  curved  lines,  the  di- 
rections of  which  can  be  varied  by  the  approach  of  bodies. 
He  has  also  shown  that  the  particles  of  solids,  as  gum  lac, 
glass,  &c.,  assume  this  character  of  polarity.  Non-con- 
ducting bodies,  through  which  the  action  of  induction 
takes  place,  are  called  dielectrics,  and  each 
of  them  has  a  specific  inductive  capacity. 
Thus,  if  three  metallic  plates,  a  b  c,  Fig. 
98,  be  insulated  parallel  to  each  other,  at- 
mospheric air  intervening  between  a  and  b, 
and  a  plate  of  gum  lac  between  b  and  e,  the 
inductive  action  of  the  gum  lac  will  be 
found  to  exceed  that  of  the  air.  The  fol- 
lowing table  gives  some  of  these  results : 

Inductive  capacity  of  air roo 

glass 1-76 

lac 2-00 

sulphur 2'24 

All  the  gases  have  the  same  inductive  capacity,  whatever 

Does  induction  take  place  in  straight  or  curved  lines  ?  Can  the  parti- 
cles of  solid  bodies  be  polarized  ?  What  are  dielectrics  ?  What  is 
meant  by  the  specific  inductive  capacity  of  dielectrics  ?  Of  air,  glass,  and 
sulphur,  what  are  the  inductive  capacities  ?  What  is  the  case  with  gas 
ecus  bodies  ? 


THE    ELECTROPHORUS.  115 

their  density,  elasticity,  temperature,  or  hygrometric  con- 
dition may  be. 

The  electrophorus  is  an  instrument  which  depends  for 
its  action  on  induction,  and  is  of  frequent  use  in  chemis- 
try. It  consists  of  a  cake  of  gum  lac  or  Fig.  99. 
sealing  wax,  b,  Fig.  99,  on  which  is  placed 
a  flat  metallic  plate,  a,  with  an  insulating 
handle,  c.  On  exciting  b  with  a  piece  of 
warm  flannel,  it  becomes  negatively  elec- 
tric, and  a  being  placed  on  it,  and  the 
finger  brought  near,  a  negative  spark, 
driven  from  a  by  the  repulsive  influence  of  b,  is  received. 
On  lifting  a  by  its  insulating  handle,  a  positive  spark  is 
obtained  ;  on  putting  it  down  on  b,  a  negative  one.  And 
in  this  manner  we  may  obtain  an  unlimited  number  of 
sparks;  positive  ones  when  a  is  lifted,  and  negative  ones 
when  it  is  down.  A  little  reflection  will  show  that  none 
of  this  electricity  comes  from  the  excited  cake  b,  but  is 
merely  the  effect  of  its  inductive  influence  on  the  electric 
condition  of  the  metallic  plate,  a.  The  electrophorus  may 
be  used  when  the  weather  is  too  damp  for  the  common 
machine  to  work. 


LECTURE  XXVIII. 

VOLTAIC  ELECTRICITY. — Of  Electricity  in  Motion. — Sul- 
zer's  Experiment. — Galvanfs  Discovery. —  Volta's  The- 
ory.—  Water  is  a  compound  Body. — Description  of  a 
simple  Voltaic  Circle  and  its  Properties. — Direction  of 
the  Current . — Different  Kinds  of  Combinations. —  Use  of 
Sulphuric  Acid. —  Origin  of  the  Electricity. 

DURING  the  last  century,  a  German  author  of  the  name 
of  Sulzer  observed,  that  when  two  pieces  of  metal  of  dif- 
ferent kinds,  as  silver  and  zinc,  are  placed  one  above  and 
the  other  beneath  the  tongue,  as  often  as  their  projecting 
ends  are  brought  in  contact  a  remarkable  metallic  taste  is 
perceived.  To  explain  this  result,  he  supposed  that  some 
kind  of  vibratory  movement  was  excited  in  the  nerves  of 
the  tongue.  It  is  the  first  recorded  pnenomenon  attributa- 
ble to  Voltaic  electricity. 

Describe  the  electrophorus  ?     What  fact  was  first  described  in  Voltaic; 
electricity  ? 


116  GALVANIC    EXPERIMENTS. 

In  the  year  1790,  Galvani,  an  Italian  anatomist,  observ- 
ed the  contractions  which  ensue  when  a  metallic  commu- 
nication is  made  between  the  nerves  and  muscles  of  a 
dead  frog;  he  found,  that  if  a  single  metal  is  employed  as 
the  line  of  communication,  contractions  of  the  muscle  take 
place  whenever  the  metal  reaches  from  the  nerve  to  the 
Fig.  100.  muscle  ;  but  that  if  two  pieces 

of  different  kinds  are  used,  the 
contractions  are  much  more 
energetic.  Thus,  if  we  take 
the  skinned  hind  legs  of  a  frog, 
Fig.  100,  hanging  together  by 
a  piece  of  the  spine,  around 
which  tin  foil  has  been  twist- 
ed, every  time  that  we  simul- 
taneously touch  the  tin  foil  and 
tlie  muscle  with  a  bent  copper  wire,  or  with  a  copper  and 
zinc  wire,  C  Z,  conjointly,  a  convulsive  contraction  takes 
place. 

To  explain  this  effect,  Galvani  supposed  that  the  mus- 
cular system  of  animals  is  constantly  in  a  positively  elec- 
trical state,  while  the  nervous  system  is  negative.  In  the 
same  manner,  therefore,  that  a  discharge  takes  place  in 
the  case  of  a  Leyden  vial,  when  a  line  of  communication 
is  opened  between  the  two  coatings,  the  muscular  con- 
tractions in  this  case  are  to  be  accounted  for.  For  some 
time  these  phenomena  went  under  the  name  of  animal 
electricity  ;  they  subsequently  have  received  the  designa- 
tions of  Galvanism  and  Voltaic  electricity. 

But  Vplta,  another  Italian  philosopher,  was  led  to  sup- 
pose that  the  cause  of  this  remarkable  result  is  not  due  to 
any  peculiarity  of  the  animal  system,  but  to  the  contact 
of  the  pieces  of  metal  employed.  This  led  to  the  inven- 
tion of  the  Voltaic  pile,  an  instrument  which  has  achieved 
a  complete  revolution  in  chemistry. 

It  is  interesting  to  remark  what  great  results  may,  in 
the  hands  of  a  true  philosopher,  spring  from  the  most  in- 
significant observations.  The  convulsive  spasms  of  a 
frog's  leg  have  ended  in  showing  that  the  entire  crust  of 
the  earth  is  ma£e  up  of  metallic  oxides,  have  revealed  the 

What  was  the  fact  discovered  by  Galvani  ?  In  what  manner  did  ht 
explain  it  ?  Under  what  names  did  these  phenomena  successively  pass  ^ 
What  was  Volta's  supposition  ? 


THE    SIMPLE    CIRCLE.  117 

mystery  why  the  magnetic  needle  points  to  the  north, 
and  revolutionized  the  science  o£  chemistry. 

What  we  have  already  said  in  the  foregoing  Lectures 
respecting  electricity  refers  chiefly  to  that  agent  in  a  mo- 
tionless or  stagnant  state,  as  the  mode  of  its  distribution 
on  conductors,  the  action  of  the  Leyden  vial,  &c.  The 
phenomena  of  Voltaic  electricity  are  those  which  arise 
from  electricity  in  a  state  of  motion. 

From  the  great  advances  which  these  sciences  have  re- 
cently made,  we  are  able  to  present  the  various  topics  in- 
volved in  a  much  clearer  way  than  by  merely  tracing 
them  in  a  historical  sketch.  I  shall  not,  therefore,  pur- 
sue the  order  in  which  these  facts  were  successively  dis- 
covered, but  present  them  in  what  now  appears  the  sim- 
plest manner. 

It  is  to  be  admitted,  though  of  that  abundant  proof 
will  soon  be  given,  that  water  is  not  a  simple,  but  a  com- 
pound body ;  that  it  consists  of  two  elements,  oxygen  and 
hydrogen  gases.  It  is  also  to  be  understood  that  metallic 
2inc  may  be  amalgamated  or  united  with  quicksilver,  by 
putting  it  in  contact  with  that  fluid  metal,  under  the  sur- 
face of  dilute  sulphuric  acid.  Strips  of  zinc  thus  amalga- 
mated exhibit  a  pure  metallic  brilliancy. 

If,  now,  we  take  a  strip  of  amalgamated  zinc,  an  inch 
wide  and  three  or  four  inches  long,  and  a  piece     Fis  101 
of  clean  copper  of  similar  size,  z  and  c,  Fig. 
101,  and  placing  them  side  by  side  in  a  glass,  f^ 
containing  water  slightly  acidulated  with  sul- 
phuric acid,  we  have  one  of  the  forms  of  a  sim- 
ple Voltaic  circle.     In  this,  it  is  to  be  observed, 
that  so  long  as  the  metallic  plates  remain  with- 
out touching  each  other,  no  remarkable  phe- 
nomenon appears ;  but  if  we  take  a  metallic  rod,  d,  and 
let  it  connect  the  top  of  the  zinc  and  copper  together,  a 
series  of  new  facts  arises. 

First,  from  the  surface  of  the  copper,  bubbles  of  gas  are 
evolved  ;  they  are  minute,  but  so  numerous  as  to  make 
the  water  turbid  ;  if  collected,  they  are  found  to  be  hydro- 
gen gas. ^ 

"What  is  the  difference  between  common  and  Voltaic  electricity?  la 
water  a  simple  or  a  compound  body  ?  What  is  meant  by  amalgamated 
zinc  ?  Describe  a  simple  Voltaic  circle.  As  long  as  the  plates  are  not  in 
contact,  does  any  phenomenon  take  place  ?  On  communicating  by  a  me- 
tallic rod,  what  gas  is  evolved  from  the  copper  ? 


118  PHENOMENA    OF    A   SIMPLE    CIRCLE. 

Secondly,  the  plate  of  zinc  rapidly  wastes  away,  as  is 
easily  proved  by  weighing  it  from  time  to  time ;  and  on 
examining  the  liquid  in  the  cup,  we  discover  the  cause  of 
this  waste,  for  that  liquid  contains  oxide  of  zinc  ;  coupling 
this  fact  with  the  former,  we  infer  that,  so  long  as  the  me- 
tallic rod,  d,  is  in  its  place,  water  is  decomposed,  its  oxy- 
genuniting  with  the  zinc,  its  hydrogen  escaping  from  the 
copper.  On  removing  the  rod,  d,  all  these  phenomena  at 
once  cease. 

Thirdly,  if,  instead  of  a  metallic  rod,  d,  a  rod  of  glass, 
or  other  non-conductor  of  electricity,  be  employed,  no  de- 
composition takes  place.  This,  therefore,  indicates  that 
the  agent  which  is  in  operation  is  electricity. 

Fourthly,  if  for  the  line  of  communication,  d,  a  piece 
of  metal  be  employed,  and  we  cautiously  lift  it  from  the 
zinc  or  copper  plate,  the  moment  the  contact  is  broken, 
in  a  dark  room  we  see  a  minute  electric  spark.  It  has 
been  already  observed  that  the  electric  spark  can  not  be 
confounded  With  any  other  natural  phenomenon. 

Fifthly,  if  the  line  of  communication  be  a  very  slender 
platinum  wire,  as  long  as  it  remains  in  its  position,  its  tem- 
perature rises  so  high  that  it  becomes  red  hot,  and  may  be 
kept  so  for  hours  together.  Now,  recollecting  that  the 
ignition  and  fusion  of  metals  take  place  when  they  are 
made  to  intervene  between  the  coatings  of  a  Leyden  vial, 
and  considering  all  the  facts  which  have  just  been  set 
forth,  we  see  that  the  following  conclusion  may  be  drawn  : 
that  in  an  active  simple  Voltaic  circle  water  is  decom- 
posed, its  oxygen  going  to  the  zinc  and  its  hydrogen  to 
the  copper,  and  that  a  continuous  current  of  electricity 
accompanies  this  decomposition,  running  from  one  metal 
to  the  other,  through  the  connecting  rod. 

The  direction  of  this  current  may  be  determined  by 
several  processes;  it  is  as  follows:  the  electricity,  leaving 
the  surface  of  the  zinc,  passes  through  the  liquid  to  the 
copper,  then  moves  through  the  connecting  wire  back 
again  to  the  zinc,  performing  a  complete  circuit ;  hence 
the  term  Voltaic  circle. 

Simple  Voltaic  circles  are  of  several  kinds ;  that  which 

What  happens  to  the  zinc  ?  Why  do  we  infer  that  water  is  decom- 
posed 1  If  a  glass  rod  is  used  instead  of  a  metallic  one,  what  is  the  result  ? 
How  can  a  spark  be  mads  visible  ?  Can  a  platinum  wire  be  ignited  ? 
From  these  facts,  what  conclusions  may  be  drawn  ?  What  is  the  course 
of  the  current  ? 


ELECTROMOTIVE    SOURCE.  119 

we  have  been  considering  consists  of  two  different  metals 
with  one  intervening  liquid,  but  similar  results  can  be  ob- 
tained with  one  piece  of  metal  and  two  different  liquids. 

In  the  foregoing  experiment,  we  have  used  dilute  sul- 
phuric acid:  this  acid  discharges  a  subsidiary  duty.  Zinc, 
when  it  oxidizes,  is  covered  with  a  coating  impermeable 
to  water  and  air ;  it  is  this  grayish  oxide  which  protects 
the  common  sheet  zinc  of  commerce  from  farther  change. 
When,  therefore,  a  Voltaic  pair  gives  rise  to  a  current  by 
the  oxidation  of  its  zinc,  that  current  would  speedily  stop 
were  not  the  oxide  removed  as  fast  as  it  forms ;  this  is 
done  by  the  sulphuric  acid,  which  forms  with  it  a  sul- 
phate of  zinc,  a  substance  very  soluble  in  water,  and  the 
metal  thus  continually  presents  a  clear  surface  to  the  water. 

As  to  the  immediate  cause  which  gives  rise  to  the  Vol- 
taic current,  there  has  been  a  difference  of  opinion  among 
chemical  authors.  Volta  believed  that  the  mere  contact 
of  the  metals  was  the  electromotive  source,  and  endeav- 
ored to  prove,  by  direct  experiment,  that  if  a  piece  of 
copper  and  zinc  are  brought  in  contact  and  then  sepa- 
rated, they  become  excited,  the  one  positively,  and  the 
other  negatively ;  upon  these  principles,  he  was  led  to  the 
discovery  of  the  Voltaic  battery.  But  many  facts  have 
now  indisputably  shown  that  the  origin  of  the  current  is 
to  be  sought  in  the  chemical  changes  going  on ;  and  in 
the  instance  we  have  had  under  consideration,  it  is  due 
to  the  decomposition  of  water.  That  the  electromotive 
action  does  not  depend  on  the  contact  of  the  metals,  seems 
to  be  proved  by  the  fact  that,  by  changing  the  nature  of 
the  liquid  intervening  between  them,  we  can  change  the 
current  both  in  direction  and  force. 

What  other  kinds  of  Voltaic  circles  are  there  ?  What  is  the  use  of 
sulphuric  acid  in  these  combinations  ?  What  was  Volta's  opinion  as  to 
the  electromotive  source  ?  What  is  the  view  now  taken  ?  What  argu- 
ments may  be  adduced  for  its  correctness  ? 


120 


THE    VOLTAIC    PILE. 


LECTURE  XXIX. 

EFFECTS  OF  VOLTAIC  ELECTRICITY. — Invention  of  the  Vol- 
taic Pile. — Cruickskank's  Trough. — Hare's  Battery. — 
Smee's  Simple  and  Compound  Battery. — Grove's  Batte- 
ry.—* Voltaic  Effects,  the  Spark,  Deflagration  of  Metals. 
— Ignition  of  Wires. — Arc  of  Flame. — Decomposition 
of  Water. — Nature  of  the  Gases  evolved. 

IT  has  been  already  observed  that,  in  the  discussions 
which  arose  respecting  animal  electricity,  Volta  attributed 
the  action  entirely  to  the  metals  employed  ;  and  reasoning 
on  this  principle,  he  concluded  that  the  effect  ought  to  in- 
crease, if,  instead  of  using  a  single  pair  of  metals,  a  great 
number  of  alternations  were  employed.  Accordingly,  on 
taking  thirty  or  forty  silver  coins  and  discs  of  zinc,  and 
pieces  of  cloth  moistened  with  acidulated  water,  of  the 
Fig.  102.  same  size,  and  arranging  them  in  a  pile  or 
"  column,  carefully  observing  to  place  them  in 
the  same  order,  silver,  cloth, .  zinc — silver, 
cloth,  zinc,  &c.,  he  found  his  expectation  ver- 
ified. On  touching,  with  moistened  hands, 
the  ends  of  the  pile,  a  shock  was  at  once  re- 
ceived, and  on  making  them  communicate 
by  a  piece  of  wire,  an  electric  spark  passed.  This  instru- 
ment, Fig.  102,  is  the  Voltaic  pile. 

From  the  important  uses  to  which  the  pile  was  soon 
devoted,  it  became  necessary  to  have  it  under  a  more  con- 
venient form.  There  are  several  inconveniences  attend- 
ing the  original  construction :  it  is  liable  to  overset,  is 
troublesome  to  put  in  action,  and  requires  to  be  taken  to 
pieces  and  carefully  cleaned  every  time  it  is  used  ;  its 
maximum  effect  lasts  but  a  short  time,  owing  to  the  weight 
of  the  superincumbent  column  pressing  out  the  moisture 
from  the  lower  pieces  of  cloth ;  and  as  soon  as  they  become 
dry,  all  action  ceases. 

These  difficulties  were  avoided,  to  a  great  extent,  in  the 
trough  battery,  which  soon  replaced  the  former  instru- 
ment. It  consists  of  a  box,  or  trough,  Fig.  103,  three  or 

How  was  Volta  led  to  the  invention  of  the  pile  ?  Describe  the  Voltaic 
pile  ?  What  are  its  effects  ?  What  inconveniences  are  there  in  the 
original  form  ? 


CRUIKSHANKS,  HARE*S,  AND  DANIELI/S  BATTERIES.   121 


Fig.  103. 


four  inches  square  at 
the  ends,  and  a  foot  or 
more  long ;  grooves 
are  made  in  the  sides 
and  bottom  of  this 
box,  and  into  them 
pieces  of  zinc  and  cop-  ^ — - — •— • 

per,  soldered  face  to  face,  are  fastened,  water  tight,  by 
cement.  These  grooves  are  about  half  an  inch  apart,  and 
into  their  interstices  acidulated  water  is  poured,  care  be- 
ing taken  that  the  metals  are  arranged  in  the  same  direc- 
tion, so  that  if  the  series  begins  with  a  copper  plate  it 
ends  with  a  zinc.  The  apparatus  is  obviously  equivalent 
to  Volta's  pile  laid  on  its  side,  and  the  facility  for  charg- 
ing it,  and  removing  the  acid  when  the  experiments  are 
over,  is  very  great.  From  the  extremities  two  flexible 
copper  wires  pass;  they  are  called  the  polar  wires,  or  elec- 
trodes of  the  battery. 

Some  very  convenient  form-s  of  Voltaic  battery  have 
been  invented  by  Dr.  Hare.  In  one  of  these,  the  liquid 
is  poured  off  and  on  the  plates  by  a  quarter  revolution  of 
a  handle ;  in  others,  the  trough  is  made  movable,  so  that 
it  lifts  up  -when  all  the  arrangements  are  ready,  ami  the 
plates  are  immersed. 

When  it  is  required  to  have  a  current,  the 
intensity  of  which  remains  constant  for  a  length 
of  time,  Daniell's  battery  is  to  be  preferred. 
It  consists  of  a  copper  cylinder,  C,  Fig.  104, 
in  which  a  solution  of  sulphate  of  copper  is 
poured  ;  within  this  is  a  second  cylinder,  P,  of 
porous  earthen-ware,  filled  with  dilute  sul- 
phuric acid,  A,  into  which  an  amalgamated 
zinc  rod,  Z,  dips.  From  the  copper  and  zinc, 
rods  project,  terminated  by  binding  ^Sljews, 
with  which  the  polar  wires  may  be  connected. 

Smee's  battery  is  also  a  very  valuable  rom- 
bination;  it  consists  of  a  plate  of  platinized 
silver,  or  platinized  platinum,  S,  Fig.  10/5,  on  each  side 
of  which  are  placed  parallel  plates  of  amalgamated  zinc, 
Z ;  these  plates  are  held  tightly  against  a  piece  of  wood, 

Describe  the  trough  battery.  Describe  some  of  the  improvements  in 
the  battery.  What  are  the  forms  introduced  by  Hare,  Duniell.  Smee,  and 
Grove  respectively? 

L 


Fig.  104. 


122 


SMEE  3  AND  GROVES  BATTERIES. 


Fig.  105. 


w,  by  means  of  a  clamp,  b,  to  which,  and 
also  to  the  silver  plate,  binding  screws, 
for  the  purpose  of 'fastening  polar  wires, 
are  affixed.  The  whole  is  suspended, 
by  means  of  a  cross  piece  of  wood,  in  a 
jar  containing  dilute  sulphuric  acid. 

Smee's  compound  battery,  represent- 
ed in  Fig.  106,  is  nothing  more  than  a 
series  of  the  foregoing  simple  circles. 
The  figure  shows  one  containing  six 
cells  ;  the  position  of  the  platinized  sil- 
ver and  zinc  plates  of  one  of  the  pairs 
is  seen  at  S  and  Z.  It  is  to  be  charged 
with  dilute  sulphuric  acid. 

Fig.  106. 


Probably  the  most  powerful  of  all  Voltaic  combina- 
Fig.  107.  tions  is  the  instrument  invented  by  Mr.  Grove. 
It  consists  of  two  metals  and  two  liquids,  amal- 
gamated zinc  and  platina,  dilute  sulphuric  acid 
and  strong  nitric'acid.  A  jar,  P,  Fig.  107,  three 
quarters  of  an  inch  in  diameter,  and  made  of 
porous  or  unglazed  earthen-ware,  is  to  be  filled 
with  strong  nitric  acid,  N,  and  in  it  a  slip  of  pla- 
tina is  placed ;  this  porous  earthen-ware  cup  is 
then  set  in  a  glass  cup,  A,  nearly  three  inches  in 
diameter;  in  this  is  placed  a  plate  of  zinc,  Z,  one 
eighth  ^of  an  inch  thick,  and  of  such  a  size,  as 
respects  its  other  dimensions,  that  it  will  readily 
pass  between  the  porous  cup,  P,  and  the  glass. 


In  the  glass,  A,  is  placed  dilute  sulphuric  acid. 

In  this  manner  several  cups  are  to  be  provided,  the  ar- 
rangement being,  zinc  in  contact  with  dilute  sulphuric 
acid,  and  platina  in  contact  with  strong  nitric  acid,  with  a 
porous  cup  intervening  between.  The  workman  also 


DEFLAGRATION    OF    METALS.  123 

previously  connects  each  zinc  cylinder  with  the  slip  OT 
platina,  which  is  in  the  next  cup,  by  soldering  between 
them  a  strip  of  copper. 

Grove's  battery  owes  its  force  to  the  decomposition  of 
water  by  zinc.  But  the  hydrogen  is  not  evolved  from  the 
surface  of  the  platina,  as  it  would  be  in  a  single  circle ; 
it  is  here  taken  up  by  the  nitric  acid,  which  undergoes 
rapid  deoxidation,  and  therefore,  during  the  use  of  this 
battery,  volumes  of  deutoxide  of  nitrogen  are  evolved. 
A  battery  of  fifty  cups  gives  rise  to  very  striking  effects  ; 
but  five  or  ten  are  quite  sufficient  to  repeat  all  the  follow- 
ing experiments. 

On  separating  the  polar  wires  of  such  a  battery  from 
each  other,  a  brilliant  spark  passes,  and,  if  the  separation 
be  gradual,  a  flame  constantly  proceeds  from  one  to  the 
other ;  the  light  of  which,  when  the  wires  are  of  copper, 
is  of  a  beautiful  green  color. 

If,  on  the  surface  of  some  quicksilver  Fig.  108. 

contained  in  a  glass,  Fig.  108,  we  low- 
er a  thin  piece  of  steel,  or  iron  wire, 
connected  with  one  of  the  poles  of  the 
battery,  the  mercury  being  kept  in  con- 
tact with  the  other,  the  steel  takes  fire 
and  deflagrates  beautifully,  emitting 
bright  sparks,  arid  the  mercury  is  rap- 
idly volatilized. 

When  thin  metal  leaves  are  made  to  intervene  between 
the  polar  wires,  they  are  at  once  dissipated,  the  flames 
they  emit  being  of  different  colors  in  the  case  of  different 
metals. 

If  a  piece  of  platinum  wire  is  made  the  channel  of 
communication  from  one  pole  to  the  other,  if  it  does  not 
fuse  at  once,  it  becomes  incandescent,  and  remains  so  as 
long  as  the  instrument  is  in  activity. 

"When  the  polar  wires  are  terminated  by  pieces  of  well- 
burned  charcoal,  or  that  variety  of  carbon  which  is  formed 
in  the  interior  of  gas  retorts,  the  light  which  passes  between 
them  when  they  are  removed  from  contact  is  one  of  the 

What  are  the  chemical  effects  taking-  place  in  Grove's  hattery  ?  On 
separating  the  polar  wires  of  a  battery,  what  phenomenon  arises  ?  How 
may  iron  wire  be  deflagrated  ?  What  phenomenon  is  seen  during  the 
deflagration  of  metallic  leaves  ?  When  a  thin  platinum  wire  communicates 
between  the  poles,  what  is  the  result  ?  How  is  the  arc  of  light  formed, 
and  what  are  its  properties  ? 


124  DECOMPOSITION    OF    WATER. 

most  brilliant  that  can  be  obtained  by  any  artificial  means. 
With  powerful  batteries,  the  pieces  of  charcoal  may  be  sep- 
Fig.  109.  arated  several  inches  apart  without  the 

^^^^&S^^^—  light  ceasing,  and  then  it  moves  from 
^^^^B  one  to  the  other  pole  in  an  arched  form, 
Fig.  109,  the  convexity  of  the  arc  being  upward.  This 
form  is  due  to  the  current  of  hot  air  which  rises  from  the 
ignited  space  between  the  poles,  and  the  light  may  be 
blown  out  by  the  mouth,  just  in  the  same  manner  that  we 
blow  out  a  candle. 

But,  in  a  scientific  point  of  view,  by  far  the  most  inter- 
esting experiment  to  be  made  with  the  Voltaic  battery  is 
Fig.  no.  the  decomposition  of  water.     Through 

the  bottom  of  a  glass  vase,  or  dish,  at 
the  point  a  Z>,  Fig.  110,  two  platinum 
wires  are  introduced,  water-tight ;  they 
pass  into  the  vase,  as  a  c,  b  d,  parallel 
to  each  other,  but  not  touching.  Over 
each  of  these  wires  a  tube  is  to  be  in- 
verted ;  the  tube  e  over  c,  andy  over  d, 
the  vase  and  the  tubes  being  previous- 
ly filled  with  water  acidulated  slightly,  to  improve  its 
conducting  power.  Now  let  the  wire  a  c  be  connected 
with  the  positive  pole  of  the  Voltaic  battery,  and&  d  with 
the  negative ;  bubbles  of  gas  in  a  torrent  arise  from  their 
extremities,  and  pass  upward  in  the  tubes,  displacing  the 
water.  The  quantity  of  gas  thus  collecting  in  th.e  two 
tubes  is  unequal,  and  whenever  we  stop  the  decomposi- 
tion there  will  be  found  iny  double  the  quantity  which  is 
in  e.  When  a  sufficient  amount  is  collected,  let  the  tube 
et  containing  the  smaller  portion  of  gas,  be  cautiously  re- 
moved, preventing  any  atmospheric  air  from  getting  into 
its  interior,  by  closing  it  with  the  finger,  and  then,  turning 
the  tube  upside  down,  let  a  stick  of  wood,  with  a  spark 
of  fire  on  its  extremity,  be  immersed  in  the  gas.  In  a 
moment  the  wood  bursts  into  a  flame,  proving  that  this  is 
oxygen  gas.  Then  take  the  other  tube,  and  allow  to  pass 
into  it  a  quantity  of  atmospheric  air  equal  to  the  volume 
of  gas  it  already  holds ;  remove  the  finger  and  apply  a 
light,  and  there  is  an  explosion.  But  this  is  the  property 

Describe  the  process  for  the  decomposition  of  water.  What  is  the  rel- 
ative proportion  of  the  gases  collected?  How  can  it  be  proved  that  the 
less  quantity  is  oxygen  and  tbe  larger  hydrogen? 


POLAR    DECOMPOSITION.  125 

of  hydrogen  gas.  We  therefore  conclude  that  in  this  ex- 
periment water  has  been  decomposed  and  resolved  into 
its  constituent  ingredients,  oxygen  and  hydrogen;  and, 
farther,  that  in  water  there  is,  by  vol-  Fig 

ume,  twice  as  much  hydrogen  as  there 
is  oxygen  gas.  The  separation  of  the 
two,  is  perfect,  so  much  so  that  the  de- 
composition may  be  conducted  in  differ- 
ent vessels.  Thus,  let  N  and  P  be  tubes, 
through  the  closed  upper  ends  of  which 
platinum  wires  pass  ;  invert  them  in 
glasses  of  water,  with  a  siphon  of  large 
bore  connecting  them.  On  making  N 
communicate  with  the  negative,  and  P  with  the  positive 
pole,  decomposition  ensues,  hydrogen  gas  accumulating  in 
N,  and  oxygen  in  P. 


LECTURE  XXX. 

THE  ELECTRO-CHEMICAL  THEORY. —  Theory  of  the  Decom- 
position of  Water. — Decomposition  of  Metallic  and  other 
Salts. — BecquereVs  Illustration  of  the  Formation  of  Min- 
erals.— Davy's  Discoveries. — Electro-chemical  Theory. — 
'Electrolytes. — Faraday's  Theory  of  definite  Action. — 
The  Electrotype. 

THE  prominent  fact  connected  with  the  decomposition 
of  water  is  the  total  separation  of  the  constituent  elements 
on  the  opposite  polar  wires  or  electrodes.  From  the 
positive  wire  oxygen  alone  escapes,  and  from  the  nega- 
tive hydrogen;  there  is  ,no  partial  admixture,  but  the 
separation  is  perfect  and  complete. 

Though  the  polar  wires  may  be  separated  from  each 
other  by  a  considerable  distance,  the  same  result  is  uni- 
formly obtained,  and  it  is  to  be  remarked  that  the  evolu- 
tion of  gas  takes  place  on  the  wires  alone  ;  no  intervening 
bubbles  make  their  appearance  in  the  intermediate  space. 
The  principle  on  which  this  is  effected  may  be  easily  under- 

What  is  the  constitution  of  water  by  volume  ?  Do  these  polar  decom- 
positions effect  a  total  separation  of  the  bodies  ?  In  the  decomposition  of 
water,  do  any  gas  bubbles  appear  in  the  intervening  space  ? 

L  2 


126  VOLTAIC   DECOMPOSITIONS. 

stood,  by  supposing  H  H  and  O  O,  Fig.  112,  to  represent 
Fig.  112.  atoms  of  hydrogen  and  oxygen  respect- 

ively; each  pair  of  them,  therefore,  rep- 
resents a  particle  of  water.  Now,  if  we 
slide  the  upper  row  of  atoms  upon  the 
lower,  as  shown  at  h  k,  o  o,  it  is  obvious 
that  a  hydrogen  atom  will  be  set  free  at 
one  extremity  of  the  line,  and  an  oxygen  atom  at  the  oth- 
er, and  that,  as  respects  all  the  intermediate  pairs  of  atoms, 
though  they  have  changed  their  places,  yet  every  particle 
of  hydrogen  is  still  associated  with  a  particle  of  oxygen, 
constituting,  therefore,  a  particle  of  water ;  and  it  is  at  the 
extremes  of  the  line  alone  that  the  gases  are  set  free.  So 
in  the  polar  decomposition  by  the  pile,  all  the  liquid  in- 
tervening between  the  poles  is  affected,  decompositions 
and  recombinations  successively  taking  place,  the  hydro- 
gen atoms  moving  in  one  direction,  the  oxygen  in  the 
other,  finally  to  be  set  free  on  the  surface  of  the  polar 
wires. 

This  capital  discovery  of  the  decomposition  of  water 
by  Voltaic  electricity  was  originally  made  by  Nicholson 
and  Carlyle.  It  is  by  far  the  most  satisfactory  method  ot 
demonstrating  the  constitution  of  that  liquid.  After  it 
was  made  known,  any  lingering  doubts  which  still  remain- 
ed on  the  minds  of  some  chemists  in  relation  to  the  com- 
posite nature  of  water  were  speedily  removed. 

In  the  same  manner  that  water  is  decomposed  by  the 
Voltaic  battery,  so,  also,  many  metallic  and  other  salts  yield 
to  its  influence.  Thus,  if  into  ajar  containing  a  solution 
of  blue  vitriol,  the  sulphate  of  copper,  two  metallic  plates 
are  introduced  parallel  to  each  other,  and  one  of  them 
brought  in  connection  with  the  negative  and  the  other 
with  the  positive  pole  of  the  battery,  decomposition  of  the 
salt  takes  place ;  the  sulphate  of  copper  being  resolred 
into  its  constituents,  sulphuric  acid  and  the  oxide  of  cop- 
per, and  the  latter  reduced  to  the  condition  of  metallic 
copper  by  hydrogen  simultaneously  evolved  with  it,  arising 
from  the  decomposition  of  a  part  of  the  water.  In  this 
manner  the  copper  may  be  deposited,  with  a  little  care, 
under  the  fdrm  of  a  tough  metallic  mass. 

How  is  this  explained  ?  How  is  it,  if  decompositions  are  going  on  in  the 
intervening  space,  that  the  gases  are  not  there  seen  1  Can  metallic  salts 
be  in  like  manner  decomposed  ? 


BECdUERELS    EXPERIMENTS. 


127 


Fig.  114. 


If  in  a  cubical  glass  vessel  Fig.  113,  divided  into  two  par- 
titions by  a  diaphragm,  a,  Fig.  113. 
and  both  partitions  filled 
with  a  solution  of  iodide 
of  potassium,  mixed  with 
a  solution  of  starch,  and 
the  positive  and  negative 
wires  of  the  battery  intro- 
duced, decomposition  of  the  iodide  takes  place,  its  iodine 
being  evolved  at  the  positive  wire,  and  giving  with  the 
starch  a  deep  blue  color,  the  blue  iodide  of  starch,  while 
the  liquid  in  the  other  partition  remains  colorless. 

M.  Becquerel  obtained  some  very  beautiful  results  by 
the  aid  of  weak  but  long-continued  electric  currents,  illus- 
trating the  probable  mode  of  formation  of  mineral  sub- 
stances by  such  currents  traversing  the  crust  of  the  earth. 
If  we  take  a  glass  tube  bent  into  the  form 
of  a  U,  and  close  the  bended  part  with  a 
plug  of  plaster  of  Paris,  putting  in  one  of 
the  branches  a  solution  of  carbonate  of 
soda,  and  in  the  other  of  sulphate  of  cop- 
per, immersing  in  one  of  the  solutions  a 
zinc  plate,  and  in  the  other  a  copper, 
connected   together  by  a  piece  of  bent 
wire,  the    liquids  communicate   through 
the  porous  plug,  and  crystals  of  the  dou- 
ble carbonate  of  copper  and  soda  form  on  the  plate  im 
mersed  in  the  copper  liquid.     In  the  same      Fig.  115. 
manner,  other  compound  salts   and  mineral 
bodies  may  be  produced. 

Or  if  we  take  ajar,  A,  and  fill  it  with  a  so- 
lution of  nitrate  of  copper  to  a,  and  then  with 
dilute  nitric  acid  to  B,  and  immerse  in  it  a  slip 
of  copper,  C  D,  presenting  equal  surfaces  to 
the  two  liquids,  an  electric  current  is  genera- 
ted,  the  copper  is  dissolved  in  the  upper  solu- 
tion, and  is  deposited  in  crystals  at  D  in  the 
lower. 

As  in  this  manner  water  and  various  saline  bodies  un- 


Describe  the  polar  decomposition  of  iodide  of  potassium.  Can  decom- 
positions be  produced  by  very  feeble  Voltaic  currents  ?  Describe  some 
of  the  arrangements  of  M.  Becquerel  for  illustrating  the  probable  mode  of 
formation  of  minerals. 


128  ELECTRO-CHEMICAL   THEORY. 

dergo  decomposition  by  the  action  of  the  pile,  it  occurred 
to  Sir  H.  Davy  that  probably  other  substances,  at  that  time 
supposed  to  be  simple,  might  also  be  decomposed.  He 
accordingly  subjected  the  alkaline  and  earthy  bodies,  then 
reputed  to  be  elementary,  to  the  influence  of  a  powerful 
battery,  and  found  that  his  supposition  was  verified.  On 
placing  a  fragment  of  caustic  potash  between  the  poles,  it 
immediately  melted ;  from  the  positive  oxygen  gas  es- 
caped in  bubbles,  and  from  the  negative,  small  metallic 
globules,  having  the  appearance  of  quicksilver,  emerged ; 
these  were  characterized,  however,  by  the  singular  qual- 
ities of  an  intense  affinity  for  oxygen,  so  that  they  would 
take  fire  on  being  touched  by  water,  or  even  ice,  and 
were  so  light  as  to  swim  upon  the  surface  of  that  liquid. 

The  result  of  Davy's  experiments  proved  that  the  al- 
kaline substances  and  all  the  earths  are  oxidized  bodies, 
and  in  most  instances  oxides  of  metals. 

On  these  principles,  Davy  established  a  division  of  ele- 
mentary bodies  into  electro-positive  and  electro- negative 
substances.  The  former  are  those  which,  during  a  polar 
decomposition,  go  to  the  negative  pole,  and  the  latter  those 
that  go  to  the  positive.  The  electro-chemical  theory  as- 
sumes that  all  bodies  have  a  natural  appetency  for  the  as- 
sumption of  the  positive  or  negative  states  respectively,  and 
that  all  the  phenomena  of  chemical  combination  are  mere- 
ly cases  of  the  operation  of  the  common  law  of  electrical 
attraction ;  for  between  particles  in  opposite  states  at- 
traction ought  to  take  place,  and  when  in  a  compound 
body,  such  as  water,  which  consists  of  particles  of  nega- 
tive oxygen  and  positive  hydrogen,  the  poles  of  an  active 
Voltaic  battery  are  immersed,  they  will  effect  its  decom- 
position, the  negative  oxygen  going  to  the  positive  pole 
and  the  positive  hydrogen  to  the  negative  pole. 

Davy's  theory  thus  not  only  accounts  for  the  decom- 
posing agencies  of  the  battery,  but  also  for  all  common 
cases  of  chemical  combination,  referring  both  to  the  fun- 
damental law  of  electric  attraction.  With  all  its  simplic- 
ity, it  would  be  very  easy  to  show,  however,  that  it  is 
founded  on  a  groundless  assumption,  and  can  not  account 
for  a  great  number  of  well-known  facts. 

What  were  the  discoveries  of  Davy  respecting  the  alkaline  and  earthy 
bodies  ?  What  is  meant  by  the  electro-chemical  theory  ?  Does  this  the- 
ory also  account  for  chemical  combination  ? 


THE    ELECTROTYPE.  129 

The  Voltaic  pile  can  not  decompose  all  bodies  indis* 
criminately.  An  electrolyte — for  so  a  decomposable  sub- 
stance is  termed — must  always  be  a  fluid  body.  It  also 
appears  that  all  electrolytes  must  have  a  binary  constitu- 
tion, or  contain  one  atom  of  each  of  their  two  constituent 
ingredients. 

Mr.  Faraday  discovered  that  the  action  of  an  electric 
current  in  effecting  the  decomposition  of  various  bodies  is 
perfectly  definite  :  thus,  if  we  make  the  same  current 
pass  through  a  series  of  vessels  containing  water,  iodide 
of  potassium,  melted  chloride  of  lead,  they  will  all  be  de- 
composed, but  in  very  different  quantities.  If  of  the  wa- 
ter there  be  decomposed  9  parts,  there  will  be  165  of 
iodide  of  potassium,  and  139  of  chloride  of  lead  ;  but 
these  numbers  represent  what  will  be  hereafter  given  as 
the  atomic  weights  of  the  bodies  in  question.  A  current 
which  can  set  free  one  grain  of  hydrogen  will  evolve  108 
of  silver,  104  of  lead,  39  of  potassium,  31*6  of  copper,  &c., 
these  being  the  atomic  weights  of  those  substances  respect- 
ively. 

A  very  beautiful  application  of  electro-chemical  decom- 
position has,  of  late,  been  introduced  into  the  arts.  It 
passes  under  the  name  of  the  electrotype.  It  consists  in 
the  precipitation  of  metallic  copper,  gold,  silver,  platina, 
&c.,  on  different  surfaces,  by  the  aid  of  a  Voltaic  current. 
Thus,  suppose  it  were  required  to  obtain  a  perfect  copy 
in  copper  of  one  of  the  faces  of  Fig.  lie. 

a  medal ;  let  a  glass  trough, 
N  C,  Fig.  116,  be  filled  with 
a  solution  of  the  sulphate  of 
copper,  and  to  the  negative 
wire,  Z,  of  a  Smee's  Voltaic 
battery,  let  the  medal  N  be  at- 
tached, all  those  portions,  ex- 
cept the  face  designed  to  be 
copied,  being  varnished  over, 
or  covered  with  wax,  to  pro- 
tect them  from  contact  with  the  liquid.  To  the  positive 
wire,  S,  let  there  be  attached  a  mass  of  copper,  C.  As 
soon  as  the  battery  is  in  action,  decomposition  of  the  sul- 

To  what  bodies  is  the  decomposing  influence  of  the  Voltaic  battery  lim- 
ited ?  Can  substances  other  than  binary  compounds  be  thus  decomposed  ? 
Explain  Faraday's  law  of  the  definite  action  of  a  Voltaic  current.  De. 
scribe  the  electrotype. 


130 


THE    VOLTAMETER. 


phate  takes  place,  metallic  copper  is  precipitated  on  the 
face  of  the  medal,  copying  it  with  surprising  accuracy. 
This  copper  is,  of  course,  withdrawn  from  the  sulphate 
in  the  solution  ;  but  while  this  is  going  on,  sulphuric  acid 
and  oxygen  are  being  evolved  on  the  mass  of  copper,  C. 
They  therefore  unite  with  it ;  and  thus,  as  fast  as  copper 
is  precipitated  on  N  by  oxydation,  new  quantities  are  ob- 
tained from  C,  and  the  liquid  keeps  up  its  strength  unim- 
paired. In  the  course  of  a  day  the  medal  may  be  re- 
moved. It  will  be  found  incrusted  with  a  tough,  red 
coat  of  copper,  which  may  be  readily  split  off  from  it.  It 
is  a  perfect  copy  of  the  surface  on  which  the  deposition 
took  place,  and,  in  turn,  it  may  be  used  as  a  mould  for 
obtaining  a  great  number  of  casts.  Gilding,  silver- 
plating,  and  platinizing  are  now  performed  on  the  same 
principles,  the  electrotype  being  one  of  the  most  beauti- 
ful contributions  which  science  has  of  late  given  to  the 
arts. 

An  instrument,  the  Voltameter,  has  been  invented  by 
Mr.  Faraday  for  measuring  quantities  of 
Voltaic  electricity.  It  is  represented  in 
Fig.  117.  It  consists  of  a  glass  jar,  b, 
filled  to  the  height  d  with  water,  and 
through  its  cover,  c,  a  graduated  tube,  a, 
passes.  In  the  lower  part  of  the  tube  at 
g,  two  pieces  of  platina  foil,  which  form 
the  terminations  of  the  polar  wires  of  the 
battery,  the  current  of  which  is  to  be 
measured,  are  introduced,  the  connection 
with  those  wirea  being  made  by  the  aid  of 
the  mercury  cups,  ef.  The  tube, «,  having 
been  filled  with  water,  as  soon  as  the  cur- 
rent passes  decomposition  takes  place,  the 
gases'  collecting  in  the  graduated  tube,  and  measuring 
the  amount  of  the  current. 


Fig.  117. 


Describe  the  Voltameter. 


DIFFERENT    VOLTAIC    BATTERIES.  131 


LECTURE  XXXI. 

OHM'S  THEORY  OF  THE  VOLTAIC  PILE. — MAGNETISM  AND 
ELECTRO-MAGNETISM.^ — Yalta's  Pile. — Hare's  Calorimo- 
tor. — Zamboni's  Pile. — Ohm's  Theory. — Electro-motive 
Force. — Resistance. — General  Law  for  the  Force  of  the 
Current. — Laws  and  Phenomena  of  Magnetism. — Elec- 
tro-magnetism, Oersteds  Discoveries  in. —  The  Galvan- 
ometer.— Electric  Rotations. —  Tangential  Force. — Elec- 
tro-magnets. 

WITH  a  given  amount  of  metallic  surface  we  can  pro- 
duce Voltaic  batteries  having  different  qualities.  Thus, 
if  we  take  a  square  foot  of  copper  and  a  square  foot  of 
zinc,  and  place  between  them  a  piece  of  wet  cloth,  we 
shall  have  a  battery  which  can  not  give  shocks,  nor  effect 
the  decomposition  of  water,  but  which  will  cause  a  fine 
metallic  wire  to  become  white  hot,  or  even  to  fuse.  If, 
again,  we  take  a  square  foot  of  copper  and  a  square  foot 
of  zinc,  and  cut  each  into  144  plates,  an  inch  square,  and 
arrange  them  with  similar  pieces  of  cloth  as  a  Voltaic 
pile,  the  instrument  will  give  shocks,  and  decompose  wa- 
ter rapidly.  From  the  same  quantity  of  metal  two  differ- 
ent species  of  battery  may  be  made ;  one  consisting  of  a 
few  plates  of  large  surface,  or  one  of  a  great  number  of 
alternations  of  smaller  plates. 

Of  these  varieties  of  battery,  the  calorimotor  of  Dr. 
Hare  is  an  example  of  the  first.  It  consists  of  a  series 
of  zinc  plates,  all  connected  together,  and  one  of  copper, 
also  similarly  connected,  constituting  therefore,  in  reality, 
a  single  pair  of  very  large  surface.  The  great  amount  of 
heat  evolved  by  this  apparatus  is  its  peculiarity. 

The  electric  pile  of  Zamboni  is  an  example  of  the  other 
kind.  It  consists  of  a  series  of  ten  or  twenty  thousand 
discs  of  gilt  paper,  alternating  with  similar  pieces  of 
very  thin  zinc  foil.  These  are  arranged  in  a  tube,  and 
kept  in  contact  by  the  pressure  of  screws  at  each  end. 
In  Fig.  118  (p.  132),  the  pile  is  laid  on  a  pair  of  gold 

What  are  the  two  principal  forms  of  battery  ?  What  do  the  oalorimo- 
tor  and  Zamboni's  pile  illustrate  ?  What  is  the  effect  produced  by  a  bat 
tery  of  large  plates  ?  What  by  one  of  many  alternations  ? 


132      OHM'S  THEORY  Of  VOLTAIC  CURRENTS. 


Fig  us.  leaf  electroscopes,  both  of 

-which  diverge,  the  one 
being  positive  and  the 
other  negative,  the  cen- 
tral parts  of  the  pile  being 
neutral.  This  instrument 
exhibits  no  calorific  ef- 
fects; its  phenomena  are 
those  of  electricity  of  high 
tension. 

These,     and,    indeed, 
"—  -—  —  =-=•*'•       ..--3gf=-»       *     many  of  the  phenomena 
of  the  electric  current,  are  clearly  accounted  for  by  the 
aid  of  Ohm's  theory  of  the  Voltaic  pile,  of  which  the  fol- 
lowing is  an  exposition  : 

1st.  By  ELECTRO-MOTIVE  FORCE  we  understand  the 
causes  which  give  rise  tp  the  electric  current;  this,  as 
we  have  explained  in  the  simple  circle,  is  the  oxidation 
of  the  zinc.  2d.  By  RESISTANCE  we  mean  the  obstacles 
which  the  current  has  to  encounter  in  the  bodies  through 
which  it  passes. 

When  we  affect  the  electric  current  in  any  portion  of 
its  path,  either  by  varying  the  electro-motive  force,  or 
changing  the  resistances,  we  simultaneously  affect  it 
throughout  the  whole  circuit;  so  that,  in  a  given  space 
of  time,  the  same  quantity  of  electricity  passes  through 
each  transverse  section  of  the  circuit. 

In  any  Voltaic  circle,  simple  or  compound,  the  force  ot 
the  current  is  directly  proportional  to  the  sum  of  all  the 
electro-motive  forces  which  are  in  activity,  and  inversely 
proportional  to  the  sum  of  all  the  resistances  ;  that  is  to 
say,  the  force  of  any  Voltaic  current  is  equal  to  the  sum 
of  all  the  electro-motive  forces,  divided  by  the  sum  of  all 
the  resistances. 

The  resistance  to  conduction  of  a  metal  wire  is  directly 
as  its  length,  and  inversely  as  its  section  ;  that  is  to  say, 
the  longer  the  wire  is,  the  greater  its  resistance,  and  the 
thicker  it  is,  the  .ess  its  resistance. 

If  we  augment  or  diminish,  in  the  same  proportion,  the 

What  is  meant  by  electro-motive  force  ?  In  a  simple  circle,  what  is  its 
origin?  What  is  meant  by  resistance  ?  On  affecting  one  part  of  a  cur- 
rent, is  the  rest  affected?  What  conclusion  is  drawn  from  that  fact? 
What  is  the  fprce  of  the  current  equal  to  ?  In  a  wire,  what  is  the  law  of 
resistance  ? 


133 

electro-motive  forces  and  the  resistances  of  a  Voltaic  cir- 
cuit, the  force  of  the  current  will  remain  the  same ;  if -we 
increase  the  electro-motive  force,  the  force  of  the  current 
increases ;  if  we  increase  the  resistance,  the  force  of  the 
current  diminishes. 

If,  in  two  Voltaic  circles  of  equal  force,  the  same  re- 
sistance is  introduced,  the  forces  of  the  currents  may  be 
enfeebled  in  very  different  proportions  ;  for  the  newly-in- 
troduced resistance  may,  in  one  of  the  circles,  bear  a  very 
great  proportion  to  the  resistances  already  existing,  and, 
in  the  other,  a  very  insignificant  proportion. 

The  following,  therefore,  is  the  general  law  which  de- 
termines the  force  of  a  Voltaic  circuit. 

1st.  The  electro-motive  force  varies  with  the  number  of 
the  elements,  the  nature  of  the  metals,  and  of  the  liquids 
which  constitute  each  element;  but  it  does  not  in  any 
manner  depend  on  the  dimensions  of  their  parts. 

2d.  The  resistance  of  each  element  of  a  Voltaic  circuit 
is  directly  proportional  to  the  distance  between  the  plates, 
as  occupied  by  the  liquid,  the  resistance  of  the  liquid  it- 
self, and  the  length  of  the  polar  wire  connecting  the  ends 
of  the  circuit ;  and  inversely  proportional  to  the  surface  of 
the  plates  in  contact  with  the  liquid,  and  to  the  section  of 
the  connecting  wire. 

3d.  The  force  of  the  current  is  equal  to  the  electro- 
motive force  divided  by  the  resistance. 

From  the  circumstance  that  lightning  has  been  repeat- 
edly known  to  render  implements  of  steel  magnetic,  and 
from  a  general  analogy  which  exists  between  the  phenom- 
ena of  magnetism  and  those  of  electricity,  it  was  long  ago 
believed  that  these  phenomena  were  due  to  one  common 
cause;  but  it  was  not  until  1819  that  their  true  relation- 
ship was  first  established  by  CErsted. 

The  phenomena  of  the  magnet  itself  were  discovered 
more  than  2000  years  ago.  The  natural  magnet,  or  load- 
stone, which  is  an  iron  ore,  possesses  the  quality  of  at- 
tracting pieces  of  iron  or  steel,  but  upon  almost  all  other 
substances  it  is  without  action.  To  hardened  steel  it  com* 

How  does  the  force  of  the  current  change  with  changes  in  the  electro- 
motive force  and  the  resistance  ?  When  a  new  resistance  is  introduced 
into  two  circles,  does  it  follow  that  both  will  be  affected  alike  ?  Give  the 
general  law  which  determines  the  force  of  the  Voltaic  current.  What  are 
the  properties  of  a  magnet  1  What  is  the  difference  of  its  action  on  iron 
and  steel  ? 

M 


134 


MAGNETISM. 


municates  its  own  properties  in  a  permanent  manner;  but 
soft  iron  is  only  transiently  magnetic,  and  as  soon  as  it  i» 
removed  from  the  influence  of  the  magnet  it  loses  its 
power.  Bars  of  steel-which  have  been  magnetized  can 
communicate  their  activity  to  other  bars  ;  they  are,  there- 
fore, of  constant  use  in  physical  investigations,  and  are  of 
two  forms,  straight  bars  and  horseshoe  magnets. 

Fig,  n9.  If  a  magnetic  bar  have  iron 

ities,  d  d,  few  orthem  being  found  in  the  middle.    If  a  piece 

Fig.  120. of  card-board  is  laid 

over  a  magnet,  and 


•K-V 


the  filings  dusted  on 
it,  they  arrange  them- 
selves in  curves,  call- 
ed magnetic  curves  ; 
there  being  in  this, 
as  in  the  former  in- 
stance, centers  of  ac- 
tion, P  P,  toward  the 
extremities  of  the 
bars,  around  which  the  curves  are  arranged.  The  ap- 
pear*nce  is  show«  in  Fig.  120. 

A  light  magnetic  bar,  S  N  so  arranged  that  it  can  be  pois- 
Fig.^i.  ed  on  a  pivot,  C,  with  free- 

dom of  motion,  is  a  magnetic 
-U  needle.  It  was  discovered 
by  the  Chinese  that  such  a 
needle,  Fig.  121,  possesses 
polarity,  or  points  north  and 
south,  a  fact  of  the  utmost 
importance  in  navigation. 
When  to  a  needle  the  poles 
of  a  bar  are  approached,  it  exhibits  attractive  and  repuls- 
ive movements.  The  law  under  which  these  take  place 
is,  "  Like  poles  repel,  and  unlike  ones  attract;"  two  north 
or  two  south  poles  repel,  but  a  north  and  a  south  attract. 

What  are  the  forms  of  artificial  magnets  ?  How  may  the  existence  of 
poles  be  shown  bv  iron  filings  ?  Describe  a  magnetic  needle.  What  is 
meant  by  its  polarity?  What  is  the  law  of  magnetic  attractions  and  re- 
pulsions ? 


ELECTRO-MAGNETISM. 


135 


Either  pole  of  a  magnet  is  attracted  by  a  piece  of  unmag- 
netized  soft  iron.  The  intensity  of  magnetic  action  is  in- 
versely proportional  to  the  square  of  the  distances. 

If  a  magnetic  needle  be  brought  into  the  neighborhood 
of  a  wire,  along  which  an  electric  current  is  passing,  the 
needle  is  at  once  disturbed  from  its  position,  and  tends  to 
set  itself  at  right  angles  to  the  wire.  The  direction  in 
which  the  transverse  movement  takes  place  depends  on 
the  relative  position  of  thevneedle  and  the  wire  ;  thus,  1st, 
if  the  wire  be  above  the  needle  and  parallel  to  it,  that 
pole  next  the  negative  end  of  the  battery  moves  west- 
ward ;  2d,  if  the  wire  be  beneath  the  needle,  it  will  move 
eastward  ;  3d,  if  the  wire  be  on  the  east  side  of  the  needle, 
the  pole  is  elevated  ;  4th,  if  on  the  west,  it  is  depressed  ; 
in  all  these  various  positions,  the  tendency  being  to  bring 
the  needle  at  right  angles,  or  transverse  to  the  wire. 

It  follows,  from  these 
facts,  that  if  a  magnet- 
ic needle  be  placed  in 
the  interior  of  a  rectan- 
gle of  wire,  Fig.  122, 
through  which  a  cur- 
rent is  made  to  flow, 
all  the  portions  of  the 
wire  conspire  to  move 
the  needle  in  the  same  direction.  The  effect,  therefore, 
becomes  much  greater  than  in  the  case  of  a  single  con- 
tinuous wire. 

On  the  same  principle,  if,  instead  of  a  single  turn,  the 


Fig.  122. 


Fig.  123. 


wire  is  repeatedly  coiled  upon  it- 
self, so  as  to  make  a  great  many 
turns,  the  effect  upon  the  needle  may 
be  greatly  increased;  and  when  the 
needle  is  made  nearly  astatic,  that 
is  to  say,  its  tendency  to  point  north 
nearly  destroyed  by  arranging  it  upon 
an  axis  with  another  needle,  similar  to  it  in  all  respects, 
but  with  its  poles  reversed,  as  N  S,  S  N,  Figure  123, 
the  directive  tendency  of  the  one  needle  neutralizing 

How  does  the  intensity  of  magnetic  action  vary  ?  In  what  does  CEr- 
Bted's  discovery  consist  ?  What  is  the  direction  which  the  needle  moves 
in  the  four  positions  round  the  wire  ?  What  is  the  effect  on  a  needle  in 
the  interior  of  a  rectangle  ?  What  is  the  principle  of  the  galvanometer  ? 


136 


ELECTRO-MAGNETIC    ROTATION. 


the  other,  but  both  tending  to  turn  in  the  same  direction 
by  the  current  in  the  coil  of  wire,  inasmuch  as  one  is  with- 
in the  coil  and  the  other  above  it,  the  arrangement  forms 
a  most  delicate  means  of  discovering  and  measuring  an 
electric  current.  It  is  called  a  galvanometer. 

As  action  and  reaction  are  always  equal  and  contrary, 
it  is  obvious  that,  if  a  conducting  wire  be  movable  and 
the  magnet  stationary,  the  latter  can  be  made  to  impress 
motions  on  the  former. 

Conducting  wires  can  be  made  to  revolve  round  the 
r.  124.  poles  of  a  magnet,  or  the  pole  of  a  mag- 
net round  a  conducting  wire ;  thus,  in  a 
glass  cup,  Fig.  124,  let  a  magnet,  »,  be 
fixed  vertically,  and  the  cup  filled  with 
mercury ;  by  means  of  a  loop,  «,  let  a 
conducting  wire,  £,  be  suspended,  having 
perfect  freedom  of  motion.  If  an  electric 
current  is  made  to  pass  down  this  wire 
through  the  mercury,  and  escape  by  the 
path  d,  the  wire  rotates  round  the  pole  n 
as  long  as  the  current  passes.  From  this 
and  similar  experiments,  it  therefore  ap- 
pears that  the  force  exerted  between  a  conducting  wire 
and  a  magnet  is  not  a  direct  attractive  or  repulsive  power, 
but  one  continually  tending  to  turn  the  movable  body 
round  the  stationary  one,  deflecting  it  continually,  and 
acting  in  a  tangential  direction.  Hence  it  is  sometimes 
spoken  of  as  a  tangential  force. 

If  round  a  bar  of  soft  iron  a  conducting  wire,  covered 
over  with  silk,  be  spirally  twisted,  as  in 
Fig.  125,  whenever  an  electric  current 
is  passed,  the  iron  becomes  intensely 
magnetic,  and  loses  its  magnetism  as 
«oon  as  the  current  stops.  A  bar  an 
inch  in  diameter,  bent  so  as  to  represent 
a  horseshoe,  Fig.  126,  with  a  wire  cov- 
ered with  silk  for  the  purpose  of  sepa- 
rating its  successive  strands  from  each 


Fig.  125 


On  the  same  principles,  can  the  wire  be  made  to  move  ?  Describe  a 
method  of  showing  the  rotation  of  a  wire  round  the  pole  of  a  magnet. 
What  is  the  nature  of  the  force  exerted  between  a  conducting  wire  and 
a  magnet  ?  Describe  the  construction  and  properties  of  a  straight  electro- 
magnet. 


ELECTRO-MAGNETS. 


137 


other,  may  be  made  to  give  rise  to  very 
striking  results.  Prof.  Henry,  by  a  modi- 
fication of  the  conducting  wire,  succeeded 
in  imparting  so  intense  a  degree  of  mag- 
netism to  a  piece  of  soft  iron  that  it  could 
support  more  than  a  ton  weight.  If  under 
one  of  these  ELECTRO-MAGNETS  a  dishful  of 
small  iron  nails  be  held,  the  moment  the 
current  passes,  the  nails  are  all  attracted, 
and,  while  they  are  held  by  its  poles,  may 
be  moulded,  as  it  were,  by  the  hand  in 
various  shapes,  but  as  soon  as  the  current 
stops  they  fall  off. 

It  is  upon  this  principle  of  producing 
temporary  magnetism  by  an  electric  cur- 
rent that  Morse's  electric  telegraph  depends. 


Fig.  126 


LECTURE  XXXII. 

ELECTRO-tftNAMICS THERMO-ELECTRICITY,     &C. Am- 

pere's  Discovery. — Properties  of  a  Helix. — Nature  of  the 
Magnet. — Faraday's  Discovery  of  Magnetic  Electricity. 
— Magnetic  Machines. — Faradian  Currents. —  Thermo- 
electricity.— Production  of  Heat  and  Cold  by  Electric 
Currents. —  Thermo-electric  Pairs. — Peculiarity  of  these 
Currents.  —  Electro-motive  Power  of  Heat.  —  Melloni's 
Pile  and  Thermometer. — Improvements  in  Thermo-elec- 
tric Pairs. — Animal  Electricity. — Steam  Electricity. 

SOON  after  the  relation  between  electricity  and  magnet- 
ism was  established,  M.  Ampere  discovered  that  there 
are  reactions  between  electric  currents  themselves. 

Two  electric  currents  flowing  in  the  same  direction  at- 
tract each  other,  but  two  electric  currents  flowing  in  op- 
posite directions  repel ;  or,  more  briefly,  "  Like  currents 
attract,  and  unlike  ones  repel." 

If  a  conducting  wire  be  bent  in  the  form  of  a  helix, 
its  terminations  returning  toward  its  middle,  as  shown  in 
Fig.  127,  it  exhibits  all  the  properties  of  an  ordinary  mag- 
netized bar ;  for  as  soon  as  the  current  passes,  it  points 


Describe  the  Lorseshoe  electro-magnet, 
between  electric  currents  ? 

M2 


What  is  the  law  of  reaction 


138 


PROPERTIES    OF    A    HELIX. 


Fig.  127.  north  and  south,  and  is  attracted  and  re- 
pelled by  the  poles  of  a  magnet,  just  as 
though  it  were  a  magnet  itself.  A  very 
neat  arrangement  for  illustrating  these 
results  is  seen  in  Fig.  128.  A  small  sim- 
ple circle,  consisting  of  a  zinc  and  copper 
plate,  connect-  Fig.  jgs. 

ed  together  by 
means  of  a  wire 
bent  so  as  to 
form  a  flat  coil, 
is  floated  by 

means  of  a  cork  in  acidulated 
water.  The  current  runs  round 
the  coil  in  the  direction  of  the 
aiTows,  and  the  arrangement, 
obeying  the  magnetic  influence 
of  the  earth,  turns,  with  its  plane 
pointing  north  and  south,  just  as 
a  magnet  would  do  if  introduced  into  the  interior  of  the 
coil,  in  the  position  shown  in  the  figure  by  the  dark  line. 
Ampere  infers,  from  the  analogy  of  these  instruments, 
that  the  magnet  owes  its  qualities  to  electric  currents  cir- 
culating in  it  in  a  transverse  direction.  The  directive 
action  of  the  magnetic  needle  or  the  electric  helix  depends 
on  the  reaction  of  electric  currents  circulating  in  the 
earth,  due  to  the  unequal  heating  of  its  surface  by  the 
rays  of  the  sun. 

We  have  seen  that  an  electric  current  can  develop 
magnetism  in  a  bar  of  iron  or  steel ;  in  the  former,  tran- 
sient, in  the  latter,  perma- 
nent magnetism.  Thus,  if 
the  iron  bar,  n  s,  Fig.  129, 
\n  be  placed  in  the  axis  of  a 
helix  of  copper  wire,  along 
which  a  current  is  flowing, 
the  current  develops  magnetism  in  the  bar.  It  was  dis- 
covered by  Faraday  that  the  converse  also  holds  good, 
and  that  a  magnet  can  give  rise  to  an  electric  current. 
Thus,  in  Fig,  129,  let  the  terminations  a  b  of  the  helix  c 

Describe  the  phenomena  of  the  electro-dynamic  helix,  Fig.  127.  De- 
scribe those  of  the  flat  coil.  "What  is  Ampere's  theory  of  the  nature  of 
the  magnet  ?  Can  a  magnetized  bar  be  made  to  develop  electric  currents  ? 


Fig.  129. 


MAGNETO-ELECTRIC    CURRENTS.  139 

be  brought  in  contact,  and  having  placed  a  soft  iron  bar, 
n  s,  within  it,  let  the  bar  be  made  magnetic  by  the  ap- 
proach of  a  strong  magnet.  As  n  s  assumes  the  magnetic 
condition,  it  generates  a  current,  which  runs  through  the 
helix  c;  and  if  at  this  moment  the  wires  a  b  are  drawn 
apart,  a  bright  spark,  sometimes  called  the  magnetic 
spark,  passes.  It  does  not  come,  however,  from  the  mag- 
net itself,  but  is  due  to  the  electric  current  established  in 
the  helix  by  the  disturbing  action  of  the  magnet.  If  be- 
tween the  terminations  a  b  a  slender  wire  is  placed,  it 
may  be  made  red  hot,  or  water  may  be  decomposed,  or 
any  of  the  phenomena  of  a  Voltaic  battery  may-be  exhib- 
:ted  by  the  aid  of  this  magneto-electric  current.  On  this 
principle  are  constructed  the  magneto-electric  machines, 
of  which  different  forms  have  of  late  been  so  generally 
introduced  for  the  purpose  of  the  medicinal  application  of 
electricity.  They  all  depend  essentially  on  the  principle, 
that  if  we  coil  round  a  piece  of  soft  iron  a  conducting 
wire,  as  often  as  the  iron  is  magnetized,  a  wave  of  elec- 
tricity flows  through  the  wire. 

If  two  conducting  wires  be  placed  parallel  and  near  to 
each  other,  when  an  electric  current  is  passed  through 
one  of  them  a  wave  of  electricity  flows  in  the  opposite  di- 
rection through  the  other ;  and  on  the  first  current  stop- 
ping, another  wave,  coinciding  with  it,  passes  through  the 
second  wire.  These  momentary  currents  are  all  called, 
from  the  name  of  their  discoverer,  Faradian  currents. 

If  we  take  a  bar  of  antimony,  <z,  Fig.  130,  and  one  of 
bismuth,  b,  and  having  soldered  them  end  to       Fig.  130. 
end  at  c,  pass  a  feeble  current  through  them 
in  a  direction  from  the  antimony  to  the  bis- 
muth, the  temperature  of  the  compound  bar 
rises  ;  but  if  the  current  passes  in  the  oppo- 
site direction,  cold  is  produced.     By  fixing 
thermometers  into  the  substance  of  the  bars, 
these  facts  may  be  readily  verified,  and  in  the 
latter  case,  when  water  is  placed  in  a  depres- 
sion made  for  it  in  the  bar,  and  the  reduction  of  tempera- 
ture slightly  aided,  it  can  be  frozen  by  the  electric  current. 

The   same  compound  bar  of  bismuth   and  antimony, 

What  are  the  properties  of  these  currents  ?  What  is  the  principle  of 
the  magneto-electric  machine  1  What  is  meant  by  Faradian  currents  ? 
What  is  their  direction  ?  How  may  heat  and  cold  be  produced  by  a  cur- 
rent in  a  compound  bar  ? 


140  THERMO-ELECTRIC    CURRENTS. 

having  its  extremities  connected  together  by  a  wire,  when- 
ever heat  is  applied  to  the  junction,  an  electric  current  sets 
from  the  bismuth  to  the  antimony,  and  when  cold  is  appli- 
ed, from  the  antimony  to  the  bismuth.  These  important 
facts  were  discovered  by  Seebeck  in  1822,  and  the  cur- 
rents have  been  designated  by  him  thermo-electric  currents. 

For  the  production  of  these  thermo-electric  effects,  two 
metals  are  not  necessarily  required.  One  end  of  a  thick 
metallic  wire  being  made  red  hot  and  brought  in  contact 
with  the  other,  a  current  instantly  passes  from  the  hot  to 
the  colder  portion,  and  continues  to  flow  in  diminishing 
quantities  until  the  two  ends  have  reached  the  same  tem- 
perature. Or  if  a  metallic  ring  be  made  red  hot  in  any 
limited  portion  of  its  circumference,  so  long  as  the  heat 
passes  with  freedom  to  the  right  hand  and  to  the  left, 
electric  development  does  not  appear  ;  but  if  we  touch 
with  a  cold  rod  the  hot  portion,  abstracting  thereby  a  por- 
tion of  its  heat,  a  current  in  an  instant  runs  round  it. 

It  is  not  alone  in  metals  that  these  thermo-electric  cur- 
rents can  be  induced  ;  other  solids,  and  even  liquids,  may 
originate  them.  Among  metals  associated  together,  the 
relation  often  exhibits  singular  changes.  Copper  and  iron 
form  a  very  active  couple  until  their  temperature  ap- 
proaches 800°  F. ;  the  current  then  stops,  and  on  contin- 
uing the  heat,  another  current  is  developed,  passing  in  the 
opposite  way.  The  same  takes  place  with  a  pair  of  sil- 
ver and  zinc,  at  a  temperature  of  248°  F. 

Thermo-electric  currents  generated  in  metallic  bars, 
experiencing  little  resistance  to  conduction,  have  therefore 
very  little  tension  ;  the  thinnest  stratum  of  water  is  a  per- 
fect non-conductor  to  them. 

In  any  thermo-electric  couple  the  quantity  of  electrici- 
ty evolved  depends  upon  the  temperature ;  but,  as  I  have 
shown  in  a  memoir  on  the  electro-motive  power  of  heat, 
inserted  in  the  Philosophical  Magazine  for  June,  1840,  it 
is  not  directly  proportional  to  it,  except  through  limited 
ranges  of  temperature ;  we  can  not,  therefore,  make  use 
of  these  currents  for  the  determination  of  temperatures 
with  accuracy,  on  the  hypothesis  of  the  proportionality  of 
the  quantities  of  electricity  to  the  quantities  of  heat. 

What  are  thermo-electric  currenfs?  Can  they  be  generated  by  one 
metal  only  ?  Can  they  originate  in  other  solids  besides  metals,  and  in 
liquids  1  What  is  the  action  of  a  pair  of  copper  and  iron,  and  silver  and 
zinc  ?  Why  have  they  so  little  tension  ?  Is  the  quantity  of  electricity 
evolved  proportional  to  the  temperature  ? 


THE    THERMO-ELECTRIC    MULTIPLIER. 


141 


By  joining  a  system  of  bars  alternately  together,  we 
may  reduplicate  the  effects  of  a  single  pair.  As  might 
have  been  predicted  on  the  theory  of  Ohm,  and  as  I  have 
shown  in  the  memoir  just  quoted  experimentally,  where 
the  conducting  resistance  remains  the  same,  the  quantity 
that  passes  the  circuit  is  directly  proportional  to  the  num- 
ber of  pairs.  It  is  upon  this  principle  that,  several  years 
ago,  M.  Melloni  constructed  his  thermo-electric  multiplier, 
Fig.  131.  Thirty  or  forty  pairs  of  minute  bars  of  bismuth 

Fig.  131. 


find  antimony  F  F,  with  their  alternate  ends  soldered  t<u 
gether,  are  arranged  in  a  small  space,  so  that  their  endg 
expose  an  area  not  exceeding  the  section  of  the  bulb  of  a 
common  thermometer,  the  current  that  passes  from  this 
pile  being  so  conducted,  by  means  of  wires  C  C,  as  to  de- 
flect a  magnetic  needle.  To  the  thermo-electric  pile  a  gal- 
vanometer is  therefore  attached,  as  seen  in  Fig.  132, 


What  is  the  principle  of  the  thermo-electric  multiplier  of  Melloni  ?  How 
vs  it  constructed  ? 


142 


THERMO-ELECTRIC    PAIRS. 


which  represents  the  whole  instrument  in  section  and 
perspective.  A  B  C  is  the  coil  of  the  multiplier,  its  ter- 
minal wires  endrflg  in  the  connecting  cups,  F  F'.  The 
coil  rests  on  a  plate,  D  E,  which  can  be  made  to  revolve 
by  means  of  a  wheel  and  screw  connected  with  the  but- 
ton Gr.  An  astatic  combination  of  needles  is  support- 
ed by  the  frame  Q,  M  N,  by  a  single  silk  thread,  V  L. 
To  protect  the  instrument  from  currents  of  air,  it  is  cov- 
ered with  a  glass  cylinder,  R  L,  strengthened  by  brass 
rings,  P  S,  Y  Z ;  K  T  is  the  basis  on  which  the  cylinder 
rests.  The  angle  of  deflection  of  the  needle  is  taken  as 
the  measure  of  the  temperature.  Of  all  thermometers, 
this  is  by  far  the  most  sensitive. 

I  have  introduced  certain  improvements  in  the  con- 
Fig.  133.  structi on  of  the  thermo- 

electric element.  Let 
a,  Fig.  133,  be  a  bar  oi 
antimony,  and  b  a  bar 
of  bismuth.  Let  them 
be  soldered  along  c  dt 
and  at  d  let  the  temper- 
ature be  raised  ;  a  cur- 
rent is  immediately  ex- 
cited, but  this  does  not 
pass  round  the  bars  a  b, 
inasmuch  as  it  finds  a  shorter  and  readier  channel  through 
the  metals  between  c  and  d,  as  indicated  by  the  arrows. 
Nor  will  the  whole  current  pass  round  the  bars  until  the 
temperature  of  the  soldered  surface  has  become  uniform. 
An  improvement  on  this  construction  is,  therefore,  such  as 
is  represented  at  a'  &',  which  consists  of  the  former  ar- 
rangement cut  out  along  the  dotted  lines  ;  here  the  whole 
current,  as  soon  as  it  exists,  is  forced  to  pass  along  the 
bars.  One  of  the  best  forms  of  a  thermo-electric  pair  ia 
given  at  a"  b",  where  a"  is  a  semi-cylindrical  bar  of  an- 
timony and  b"  of  bismuth,  united  by  the  opposite  corners 
of  a  lozenge-shaped  piece  of  copper,  c.  The  heat  is  to  fall 
on  c,  which  becomes  hot  and  cold  with  promptitude,  and 
determines  a  current. 

Besides  the  various  sources  of  electricity  to  which  I 
have  referred,  there  are  certain  animals  which  possess 

In  what  manner  may  the  simple  thermo-electric  pair  be  improved  T 
What  is  animal  electricity-  ? 


ANIMAL    ELECTRICITY.  143 

the  power  of  controlling  the  equilibrium  of  the  electric 
fluid  in  their  neighborhood  at  will,  being  accommodated 
for  this  purpose  with  a  specific  nervous  apparatus.  The 
torpedo,  a  fish  living  in  the  Mediterranean,  and  the  gym- 
notus  electricus,  which  is  found  in  some  of  the  fresh-wa- 
ter streams  of  South  America,  have  this  property.  The 
shock  of  the  torpedo  passes  through  conducting  bodies, 
but  not  through  non-conductors.  A  gymnotus  which  was 
exhibited  in  London  was  found  to  deflect  a  magnetic  nee- 
dle powerfully  by  its  discharge.  A  steel  wire  was  mag- 
netized by  it,  and  iodide  of  potassium  decomposed.  In  an 
interrupted  metallic  circuit  a  spark  was  seen,  and  the  in- 
duced spark  was  also  obtained  by  a  coil.  The  current 
passed  from  the  anterior  to  the  posterior  parts  of  the  animal. 
Mr.  Faraday,  the  author  of  these  experiments,  calculates 
that  the  quantity  of  electricity  passing  at  each  discharge 
of  the  fish  was  equal  to  that  of  a  Leyden  battery  contain- 
ing 3500  square  inches  charged  to  its  highest  degree,  and 
this  could  be  repeated  two  or  three  times  with  scarce  a 
sensible  interval  of  time. 

As  the  electricity  which  these  animals  discharge  de- 
pends on  their  nervous  action,  the  production  of  it  is  at- 
tended with  a  corresponding  nervous  exhaustion.  It  is, 
therefore,  not  improbable  that  the  converse  of  these  actions 
holds  good,  and  hereafter  it  will  be  found  that  electricity 
reacts  on  the  nervous  fluid. 

In  concluding  this  subject,  I  may  mention  a  source  of 
electricity  which  of  late  has  excited  much  attention.  When 
high-pressure  steam  is  allowed  to  escape  from  a  boiler 
through  a  narrow  jet,  a  powerful  excitement  is  produced, 
and  sparks  many  feet  in  length  may  be  obtained.  The 
effect  appears  to  be  due  to  the  friction  of  minute  drops  of 
water  against  the  tube  through  which  the  steam  is  es- 
caping. 

By  what  animals  is  it  exhibited  ?  What  effects  have  been  produced 
by  the  electricity  of  the  gymnotus  ?  What  is  the  computed  quantity  of 
the  electricity  in,  each  discharge  ?  Why  is  this  electric  development  at- 
tended with  a  nervous  exhaustion*  What  is  the  cause  of  electricity  pro- 
duced by  steam  ? 


PART  II, 


LECTURE  XXXIII. 

THE    NOMENCLATURE.  —  The   French   Nomenclature.  • 
Table  of  Elementary  Bodies. — Nomenclature  for  Com- 
pound Bodies,  Acids,  Bases,  and  Salts. 

UNTIL  after  the  discovery  of  oxygen  gas,  the  nomencla- 
ture of  chemistry  was  very  loose  and  complicated.  The 
trivial  names  which  were  bestowed  on  various  bodies  had 
frequently  little  connection  with  their  properties  ;  some- 
times they  were  derived  from  the  name  of  the  discoverer, 
or  sometimes  from  the  place  of  his  residence.  Glauber 
salt  takes  its  designation  from  the  chemist  who  first 
brought  it  into  notice,  and  Epsom  salt  from  a  village  in 
England,  in  which  it  was  at  one  time  made. 

It  is  obvious  that* such  a  system  of  nomenclature,  as 
soon  as  the  number  of  compound  bodies  increased,  would 
not  only  become  unmanageable,  but,  by  reason  of  the  im- 
possibility of  carrying  in  the  memory  such  a  mass  of  uncon- 
nected terms,  offer  a  very  serious  impediment  to  the  prog- 
ress of  the  science.  Lavoisier  and  his  associates,  about  the 
close  of  the  last  century,  constructed  a  new  nomenclature, 
with  a  view  of  avoiding  these  difficulties.  Its  principles, 
with  some  modifications,  are  now  universally  received. 
The  following  is  a  brief  exposition  of  it : 

Natural  bodies  may  be  divided  into  two  classes,  simple 
and  compound ;  the  former  are  also  called  elementary.  By 
simple  or  elementary  bodies  we  mean  those  which  have 
not  as  yet  been  decomposed. 

Among  simple  substances,  those  which  have  been  known 
for  a  long  time  retain  the  names  by  which  they  are  pop- 
ularly distinguished;  thus,  gold,  iron,  copper,  &c. ;  and 
when  new  bodies  belonging. to  this  class  are  discovered, 

What  was  the  nature  of  the  nomenclature  used  by  the  older  chemists  ? 
When  was  the  system  now  in  use  invented?  What  is  meant  by  simple 
or  elementary  bodies  ?  What  is  the  rule  for  the  old  simple  bodies  ?  What 
for  those  newly  discovered  ? 


NOMENCLATURE    FOR    SIMPLE    BODIES. 


145 


they  are  to  receive  a  name  descriptive  of  one  of  their 
leading  properties  ;  thus,  chlorine  takes  its  name  from  its 

freeriish  color,  and  iodine  from  its  purple  vapor.     It  is  to 
e  regretted  that  this  rule  has  often  been  overlooked. 

Some  doubt  exists  as  to  the  exact  number  of  the  ele- 
mentary bodies.  It  may  be  estimated  at  58,  including 
three  metals  recently  discovered,  the  titles  of  which  have 
not  yet  been  completely  established. 

Of  the  list  of  elementary  bodies,  the  metals  form  by  far 
the  larger  portion,  there  being  45  of  them .;  the  remaining 
13  are  commonly  spoken  of  as  non-metallic  substances. 
By  some  authors  these  are  called  metalloids,  in  contra- 
listinction  to  the  metals,  an  epithet  which,  however,  is 
very  objectionable. 

Table  of  elementary  or  simple  Substances,  with  their  Symbols  and  Atomic 
Weights. 


Non-metallic  Elemei*. 

Symbols. 

At  WtB. 

Metallic  Elements. 

Symbols. 

At  wts. 

Oxygen  .     . 

0. 

8-013 

Erbium   .     .-    .     . 

E. 



Hydrogen    . 
Nitrogen      . 

H. 

N. 

1-000 
14-19 

Terbium  .... 
Manganese      .     . 

Tr. 
Mn. 

27-72 

Sulphur  .     •         • 

S. 

16-12 

Iron    

Fe. 

27-18 

Phosphorus 

P. 

15.72 

Cobalt     .... 

Co. 

29-57 

Carbon    .     . 

c. 

6-04 

Nickel     .... 

Ni. 

29-62 

Clilorine  .     . 

Cl. 

35-47 

Zinc    

Zn. 

32-31 

Bromine  .     . 

Br. 

78-39 

Cadmium     .     .    . 

Cd. 

55-83 

Iodine      •               • 

I. 

12,6-57 

Pb. 

103-73 

Fluorine 

F. 

18'74 

Tin 

Sn 

58'92 

Boron      .     . 

B. 

10-91 

Bismuth  .... 

Bi. 

71-07 

Silicon     .     . 

Si. 

22-22 

Copper    .... 

Cu. 

31-71 

Selenium     . 

Se. 

39-63 

Uranium       .     .     . 

U. 

217-20 

Mercury  .... 

Hg. 

202-87 

Metallic  Elemen  9. 

Silver  „    .     . 

Ag. 

108-31 

Potassium  . 

K. 

39-26 

Palladium 

Pd. 

53-36 

Sodium    .     . 

Na. 

23-31 

Rhodium 

B. 

52-20 

Lithium  .     . 

L. 

6-44 

Iridium    .  •• 

Ir. 

98-84 

Barium   .     . 

Ba. 

68-66 

Platinum 

Pt. 

98-84 

Strontium    . 

Sr. 

43-85 

Gold    . 

Au. 

199-2 

Calcium  .     . 

Ca. 

20-52 

Osmium  . 

Os. 

99-72 

Magnesium       -  ;.  ' 

Mg. 

12-89 

Titanium            -    . 

Ti. 

24-33 

Aluminum  . 

Al. 

13-72 

Tantalum 

Ta. 

184-90 

Qlucinum     . 

G. 

26-54 

Tellurium 

Te. 

64-25 

Yttrium  .     . 

Y. 

32-25 

Tungsten 

W. 

99-70 

Zirconium   . 

Z. 

33-67 

Molybdenum 

Mo. 

47-96 

Thorium  .     . 

Th. 

59-83 

Vanadium 

V. 

68-66 

Cerium    .     . 

Ce. 

46.05 

Chromium 

Cr. 

28-19 

Lanthanum 

La. 



Antimony 

£b. 

6462 

Didymium   . 

D. 



Arsenic  . 

As. 

37-67 

Compound  bodies  may,  for  the  most  part,  be  divided 

What  is  the  number  of  the  elementary  bodies  ?  Of  these,  to  what  class 
do  the  greater  part  belong?  "What  are  the  symbols  for  the  elementary 
bodies  ?  What  are  their  atomic  weights  ? 

N 


146  NOMENCLATURE    FOR    COMPOUN'D^. 

into  three  groups :  acids,  bases,  and  salts.  By  an  acid 
we  mean  a  body  having  a  sour  taste,  reddening  vegetable 
blue  colors,  and  neutralizing  alkalies ;  by  a  base,  a  body 
which  restores  to  blue  the  color  reddened  by  an  acid,  and 
possessing  the  quality  of  neutralizing  the  properties  of  an 
acid  ;  by  a  salt,  the  body  arising  from  the  union  of  an  acid 
and  a  base.  These  definitions,  however,  are  to  be  receiv- 
ed with  considerable  limitation. 

The  nomenclature  for  acid  substances  is  best  seen  from 
an  example.  Thus,  sulphur  and  oxygen  unite  to  form  an 
acid :  it  is  called  sulphuric  acid ;  the  termination  in  ic  being 
expressive  of  that  fact.  But  very  frequently  two  substances 
will  form  more  than  one  acid,  by  uniting  in  different  pro- 
portions ;  in  this  case  the  termination  in  ous  is  used ;  thus 
we  have  sulphurous  acid,  so  called  because  it  contains  less 
oxygen  than  sulphuric.  The  prefix  "  hypo"  is  also  used, 
as  in  hyposulphurous  and  hyposulphuric  acids :  it  indicates 
acids  containing  less  oxygen  than  sulphurous  and  sulphuric 
acids.  The  prefix  "hyper"  is  used  in  the  same  way;  thus, 
hyperchloric  acid,  an  acid  containing  more  oxygen  than 
chloric  acid. 

With  respect  to  bases,  the  generic  termination  is  in  ide. 
If  oxygen  and  lead  unite,  we  have  oxide  of  lead,  and  in 
the  same  manner  we  have  chlorides,  bromides,  iodides, 
and  fluorides.  And  if  these  elements  form  compounds  in 
more  proportions  than  one,  we  indicate  their  proportion 
by  the  Greek  numerals  protos,  deuteros,  tritos ;  thus  we 
have  protoxides,  deutoxides,  tritoxides  ;  the  protoxide  of 
lead  contains  one  atom  of  oxygen  and  one  of  lead,  the 
deutochloride  of  mercury  two  atoms  of  chlorine  and  one 
of  mercury,  &c.  In  the  same  manner,  the  prefixes  sub, 
sesqui,  and  per  are  used;  thus,  a  suboxide  contains  the 
lowest  proportion  of  oxygen,  a  peroxide  the  highest  pro- 
portion, and  a  sesquioxide  intervenes  between  a  protoxide 
and  a  deutoxide,  its  oxygen  being  in  the  proportion  of  one 
atom  and  a  half. 

By  an  alloy,  we  mean  the  substance  arising  from  the 
union  of  two  metals ;  thus,  copper  and  zinc  unite  to  form 

Into  what  groups  may  compound  bodies  be  divided  ?  What  is  the  defi- 
nition of  an  acid  ?  What  is  a  base  ?  What  is  a  salt  ?  What  do  the  ter- 
minations ic  and  ous  indicate  ?  What  is  the  meaning  of  the  prefixes  hypo 
and  hyper  1  What  does  the  termination  ide  signify  ?  What  the  prefixes 
protos,  deuteros,  and  tritos,  sub,  sesqui,  and  per  ?  What  is  an  alloy  and 
?n  amalgam  ? 


METHOb    OF    SYMBOLS.  147 

brass,  which  is  an  alloy.  If  one  of  the  metals  is  mercury, 
the  compound  is  called  an  amalgam.  And  when  sulphur, 
phosphorus,  carbon,  and  selenium  unite  with  metals,  01 
with  each  other,  the  termination  uret  is  used;  thus  we 
have  sulphurets,  phosphurets,  carburets,  &c. 

With  respect  to  the  nomenclature  for  salts,  the  termi- 
nations ate  and  ite  are  used  to  indicate  acids  in  ic  and  ous 
respectively.  The  sulphate  of  potash  contains  sulphuric 
acid,  and  the  sulphite  of  potash  sulphurous  acid.  And 
as  we  have  already  seen  that  different  oxides  arise  by  the 
union  of  oxygen  in  different  proportions,  and  these  bodies 
frequently  give  rise  to  different  series  of  salts,  the  opera- 
tion of  the  nomenclature  may  be  readily  traced  ;  thus, 
the  protosulphate  of  iron  is  the  sulphate  of  the  protoxide 
of  iron,  but  the  persulphate  of  iron  is  a  sulphate  of  the 
peroxide,  and  the  deutosulphate  of  platinum  a  sulphate 
of  the  deutoxide  of  platinum.  When  the  relative  quan- 
tity of  the  acid  and  base  varies,  Latin  numerals  are  em- 
ployed ;  thus  the  bisulphate  of  potash  contains  two  atoms 
of  sulphuric  acid  and  one  of  potash. 

Salts  are  said  to  be  neutral  if  neither  their  acid  nor 
base  be  in  excess.     If  the  acid  predominates,  it  is  an 
or  super-salt ;  if  the  base,  it  is  a  basic,  or  sub-salt. 


LECTURE  XXXIV. 

THE  SYMBOLS. — Failure  of  the  Nomenclature  in  the  Case 
of  Complex  Compounds.  —  Failure  in  Difference  of 
Grouping.  —  Symbols  for  elementary  Bodies. —  Expres- 
sions for  several  Atoms. —  Use  of  the  Plus  Sign. — Ex- 
pressions for  Grouping. 

So  long  as  the  constitution  of  compound  bodies  is  sim- 
ple there  is  no  difficulty  in  applying  the  nomenclature,  or 
in  recognizing  from  the  name  of  the  compound  the  nature 
and  proportions  of  its  constituents.  Thus,  protoxide  of 
hydrogen  clearly  indicates  a  body  in  which  one  atom  of 
oxygen  is  united  with  one  of  hydrogen,  bisulphate  of  pot- 
ash a  body  composed  of  two  atoms  of  sulphuric  acid  and 

When  is  the  termination  uret  employed  ?  "What  do  the  terminations 
ate  and  ite  indicate  ?  What  is  the  nomenclature  for  the  salts  ?  What  is 
a  neutral  salt  1  What  is  an  acid,  or  super-salt  ?  What  is  a  basic,  or  sub- 
salt  ?  Under  what  circumstances  does  the  nomenclature  apply,  and  when 
does  it  fail  ? 


148  IMPERFECTIONS    OF    THE    NOMENCLATURE. 

one  of  potash,  and  even  in  more  complicated  cases,  such 
as  the  sulphato-tricarbonate  of  lead,  &c.,  the  same  prin- 
ciples will  serve  as  a  guide. 

But  when  compound  bodies  consist  of  a  great  number 
of  atoms,  the  nomenclature  ceases  to  be  of  any  service. 
Thus,  starch  is  composed  of  twelve  atoms  of  carbon,  ten 
of  hydrogen,  and  ten  of  oxygen.  Fibrin  is  composed  of 
forty-eight  atoms  of  carbon,  thirty-six  of  hydrogen,  four- 
teen of  oxygen,  six  of  nitrogen,  with  minute  but  essential 
quantities  of  sulphur  and  phosphorus.  On  the  principles 
of  the  nomenclature,  it  would  be  difficult  to  give  to  the 
first  a  technical  name,  and  in  the  case  of  the  latter  im- 
possible. 

The  peculiarity  of  organic  compounds  is,  that  they 
contain  but  few  of  the  elementary  bodies,  being  chiefly 
made  up  of  carbon,  hydrogen,  oxygen,  and  nitrogen  ;  but 
these,  as  in  the  case  of  fibrin,  unite  in  a  very  complicated 
way,  very  often  hundreds  of  atoms  being  involved.  The 
nomenclature  is  therefore  inapplicable  to  organic  chemistry. 

There  is  also  another  very  serious  difficulty  in  its  way. 
It  has  been  discovered  that  compounds  may  consist  of  the 
same  elements,  united  in  precisely  the  same  proportions, 
so  that  when  they  are  analyzed  they  yield  precisely  the 
same  results,  and  yet  they  may,  in  reality,  be  very  differ- 
ent substances.  Identity  in  composition  is  no  proof  of 
the  sameness  of  bodies.  Thus  we  may  have  the  same 
elements  uniting  together  in  the  same  proportion,  and 
yielding  a  solid,  a  liquid,  or  a  gas  indifferently.  This  re- 
sult may  depend  on  several  causes,  as  will  be  presently 
explained;  but  among  these  causes  I  may  here  specify  what 
is  termed  by  chemists  "  Grouping."  Thus,  suppose  four 
elementary  bodies,  A  B  C  D,  unite  together,  there  is  ob- 
viously a  series  of  compounds  which  may  arise  by  per- 
muting or  grouping  them  differently,  as  in  the  following 
example : 

1)  A  +  B  + C  +  D. 

2)  A  C       -f  B  D. 

3)  AD      -f  CB. 

&c.  &c. 

What  is  the  peculiarity  of  organic  compounds  ?  Why  is  the  nomencla- 
ture inapplicable  to  organic  chemistry  ?  Is  identity  of  composition  any 
proof  of  the  identity  of  bodies  ?  What  is  meant  by  grouping  ?  Give  an 
example. 


METHOD    OF    SYMBOLS.  149 

The  method  of  symbols  which  is  designed  to  meet  these 
difficulties,  and  is,  in  reality,  an  appendix  and  improve- 
ment upon  the  nomenclature,  was  originally  introduced 
by  Berzelius ;  but  the  form  which  is  now  most  commonly 
adopted  is  that  of  Liebig  and  Poggendorff.  The  advan 
tages  which  have  been  found  to  accrue  from  it  are  so 
great,  that  it  is  now  introduced  into  every  part  of  chemis- 
try, so  that  it  is  impossible  to  read  a  modern  work  on  this 
science  without  having  previously  mastered  the  symbols 

The  student  should  not  be  discouraged  at  the  mathe- 
matical appearance  of  chemical  formulae.  He  will  find, 
by  a  little  attention,  that  they  are  founded  upon  the  sim- 
plest principles,  and  involve  merely  the  arithmetical 
operations  of  addition  and  multiplication.  The  following 
is  a  brief  exposition  of  their  nature  : 

For  the  symbol  of  an  elementary  substance  we  take  the 
first  letter  of  its  Latin  name,  as  is  shown  in  the  table 
given  in  the  last  lecture.  Those  symbols  should  be  com- 
mitted to  memory.  But  as  it  happens  that  several  sub- 
stances sometimes  have  the  same  initial  letter,  to  distin- 
guish between  them  we  add  a  second  small  letter.  Thus, 
carbon  has  for  its  symbol  G. ;  chlorine,  CL  ;  copper  (cu- 
prum), Cu. ;  cadmium,  CcL,  &c.  It  may  be  observed  that 
in  the  case  of  recent  Latin  names  the  German  synonym 
is  always  used ;  thus,  potassium  is  called  kalium  in  Ger- 
many, and  has  for  its  symbol  K. ;  sodium  is  called  natri- 
um, and  has  for  its  symbol  Na.,  &c. 

But  a  symbolic  letter  standing  alone  not  merely  repre- 
sents a  substance ;  it  farther  represents  one  atom  of  it ; 
thus,  C  means  one  atom  of  carbon,  and  O  one  atom  of 
oxygen. 

If  we  wish  to  indicate  that  more  than  one  atom  is  pres- 
ent, we  affix  an  appropriate  figure,  as  in  the  following 
examples:  C12 .  Hw  .  010.  Thus,  nitric  acid  is  composed 
of  one  atom  of  nitrogen  united  to  five  of  oxygen,  and  we 
wiite  it  ]VO5. 

When  a  compound,  formed  of  several  compounds,  is  to 
be  represented,  we  make  use  of  an  intervening  comma ; 
thus,  strong  oil  of  vitriol  is  composed  of  one  atom  of  sulphur 

What  are  the  symbols  for  elementary  bodies  ?  "When  two  bodies  be 
gin  with  the  same  letter,  how  are  the  symbols  arranged  1  What  does  a 
single  symbol  standing  alone  represent  ?  How  are  more  atoms  than  one 
represented  ?  How  is  the  comma  employed  ? 

N  2 


150  METHOD    OF    SYMBOLS. 

and  three  of  oxygen,  united  with  one  atom  of  water,  which 
is  composed  of  one  atom  of  oxygen'  and  one  of  hydrogen, 
and  we  write  it  SO31  HO. 

If  we  desire  to  indicate  that  compounds  are  united  with 
a  feeble  affinity,  we  make  use  of  the  sign  +  ;  thus,  the 
composition  of  sulphuric  acid  may  be  written  SO3,  or 
<SO2-h  O,  the  latter  formula  implying  that  one  of  the  atoms 
of  oxygen  is  held  by  a  feebler  affinity  than  the  other  two. 

When  a  large  figure,  or  coefficient,  is  placed  on  the 
same  line  as  the  symbol,  and  to  the  left  of  it,  it  multiplies 
that  symbol  as  far  as  the  first  comma  or  -f-  sign;  or,  if  the 
formula  be  placed  in  a  parenthesis,  it  multiplies  every 
letter  under  the  parenthesis;  thus,  2<S03,  KO,  HO  or 
2SOA+KO-\-HO  mean  two  atoms  of  sulphuric  acid 
united  with  one  of  potash  and  one  of  water,  forming  the 
bisulphate  of  potash;  but  2(<SO3,  KO,  HO.)  would  repre- 
sent two  atoms  of  a  salt  composed  of  one  of  sulphuric  acid, 
one  of  potash,  and  one  of  water,  the  figure  here  multiply- 
ing all  under  the  parenthesis. 

The  advantages  which  arise  from  the  use  of  these  sim- 
ple rules  are  very  great ;  we  can,  even  with  the  most 
complex  bodies,  not  only  express  their  composition,  but 
also  the  molecular  arrangement,  or  grouping  of  their 
atoms ;  we  can  follow  them  through  the  most  intricate 
changes,  and  without  difficulty  trace  out  their  metamorph- 
oses. For  example,  analysis  shows  that  alcohol  is  com- 
posed of 

Qi  H&i  O2, 

but  many  facts  in  its  history  lead  us  to  know  that  its  mole- 
cular constitution  is 

(C<H5)0+HO; 

that  is  to  say,  it  contains  a  compound  radical  C4H5,  to 
which  the  name  of  ethyl  has  been  given,  and  this  fact 
being  understood,  we  see  at  once  that  upon  the  principles 
of  the  nomenclature  the  true  name  for  alcohol  is  the  hy- 
drated  oxide  of  ethyl ;  moreover,  alcohol  is  derived  by 
processes  of  fermentation  from  sugar.  The  constitution 
of  dry  grape  sugar  is 

^12»   -"I2»    UlZ' 

"What  is  the  use  of  the  sign  plus  ?  How  far  does  a  coefficient  multi- 
ply ?  What  are  the  advantages  arising  from  the  symbols  ?  Give  an  ex 
ample  in  the  case  of  alcohol. 


LAWS    OF    COMBINATION.  151 

This  complex  atom,  under  the  influence  of  active  yeast,  is 
split  into 

2(C4H,02) 4(00,), 

that  is  to  say,  into  two  atoms  of  alcohol  and  four  of  cat  • 
bonic  acid  gas  ;  and,  accordingly,  we  find,  during  fermen- 
tation, that  the  sugar  disappears,  alcohol  forming  in  the 
liquid,  and  carbonic  acid  gas  escapes. 

The  student  should  accustom  himself  to  the  translation 
of  the  nomenclature  into  symbols,  and  symbols  into  the 
nomenclature,  in  cases  where  it  is  possible,  for  it  is  abso- 
lutely essential  that  he  should  be  perfectly  familiar  with 
the  process. 


LECTURE  XXXV. 

THE  LAWS  OF  COMBINATION. — Law  of  Fixed  Proportions. 
— Numerical  Law. — Multiple  Law. — Modes  of  express- 
ing Composition. — Proportions,  Equivalents,  and  Atomic 
W^eights. — Relation  between  Combining  Volumes  and 
Atomic  Weights.  —  Table  of  Specific  Gravities  and 
Atomic  Weights. 

IT  has  been  shown,  in  the  first  and  second  lectures, 
that  material  substances  possess  an  atomic  constitution, 
and  all  the  phenomena  of  chemistry  bear  out  this  conclu- 
sion. It  follows,  therefore,  when  substances  combine 
with  each  other  and  give  rise  to  new  products,  the  union 
takes  place  by  the  atoms  of  the  one  associating  themselves 
with  the  atoms  of  the  other,  and  as  these  atoms  possess 
weight  and  other  properties  which  are  specific,  there  are 
certain  circumstances,  easily  foreseen,  which  must  attend 
Buch  combinations. 

1st.  The  constitution  of  a  compound  body  must  always 
be  fixed  and  invariable.  This  arises  from  the  fact  of  the 
unchangeability  of  the  properties  of  atoms  ;  one  atom  of 
water  will  always  be  composed  of  one  atom  of  oxygen 
and  one  of  hydrogen ;  one  atom  of  carbonate  of  lime  will 
always  consist  of  one  atom  of  carbonic  acid  and  one  of 
lime.  Or,  more  generally,  if  a  good  analysis  of  water  has 
shown  that  nine  grains  of  that  substance  contain  eight 

Iu  what  manner  does  the  combination  of  bodies  take  place  ?  What  is 
meant  by  the  law  of  fixed  proportions  ? 


152  NUMERICAL    AND    MULTIPLE    LAWS. 

grains  of  oxygen  and  one  of  hydrogen,  every  subsequent 
analysis  will  correspond  therewith. 

2d.  The  proportions  in  which  bodies  are  disposed  to 
unite  with  each  other  can  always  be  represented  by  cer- 
tain numbers  ;  these  numbers  being,  in  fact,  the  relative 
weights  of  their  atoms.  Thus  water  is  composed  of  an 
atom  of  oxygen  and  one  of  hydrogen,  and  inasmuch  as 
the  oxygen  atom  is  eight  times  heavier  than  that  of  hy- 
drogen, it  necessarily  follows  that  in  every  nine  parts  of 
water  we  shall  have  eight  of  oxygen  and  one  of  hydro- 
gen. These  numbers  are,  therefore,  spoken  of  as  the 
combifiing  proportion  or  equivalents  of  the  substances 
to  which  they  are  attached.  If,  farther,  we  examine, 
when  oxygen  and  sulphur  unite,  what  are  the  relative 
quantities,  we  shall  find  that  eight  parts  of  oxygen  com- 
bine with  sixteen  of  sulphur,  forming  hyposulphurous 
acid.  And  if  sulphur  and  hydrogen  unite,  it  will  be  found 
that  sixteen  of  sulphur  combine  with  one  of  hydrogen. 
In  this  manner,  by  examining  the  various  elementary 
bodies,  we  find  that  Certain  numbers  are  expressive  of  the 
proportions  in  which  they  are  disposed  to  unite,  and  these 
numbers  represent  the  relative  weight  of  their  atoms ; 
thus,  if  1  be  taken  as  the  atomic  weight  of  hydrogen,  that  of 
oxygen  is  8,  that  of  sulphur  16,  &c. ;  the  atomic  weights  of 
the  elementary  bodies  have  been  given  in  Lect.  XXXIII. 

3d.  If  two  substances  unite  with  each  other  in  more 
proportions  than  one,  those  proportions  bear  a  very  simple 
arithmetical  relation  to  one  another;  thus,  14  grains  of 
nitrogen  will  successively  unite  with  8,  16,  24,  32,  40 
grains  of  oxygen,  forming  successively  the  protoxide  of 
nitrogen,  the  deutoxide,  hyponitrous  acid,  nitrous  acid, 
and  nitric  acid.  And  when  the  numbers  expressing  the 
amount  of  oxygen  are  examined,  it  is  seen  that  they  are 
in  the  second  twice,  in  the  third  thrice,  in  the  fourth  four 
times,  and  in  the  fifth  five  times  the  amount  of  the  first; 
they  are,  therefore,  simple  multiples  of  it.  The  reason  of 
this  is  plain  when  we  write  the  constitution  of  these  bodies 
in  symbols ;  they  are  successively, 

NO. .  NO,..  NO3..NO4..NO, ; 

What  by  the  numerical  law  ?  Give  an  example  in  each  case.  What 
do  the  numbers  represent  ?  Give  examples  of  these  numbers.  What  is 
meant  by  the  multiple  law  ?  Give  an  example  of  it  in  the  case  of  the  com- 
pounds of  nitrogen  and  oxygen. 


ATOMIC    WEIGHTS    OE,    EQUIVALENTS.  153 

and  if  one  atom  of  oxygen  weighs  8,  two  must  weigh  16, 
three  24,  four  32,  &c. ;  the  multiple  law,  therefore,  is  a 
necessary  consequence  of  the  combination  of  atoms. 

Observation  has  shown  that  there  are  two  series  ac- 
cording to  which  bodies  may  unite  with  each  other. 

(1.)  1  atom  of  A  may  unite  with  1,  2,  3,  4,  5,  &c.,  atoms  of  B. 
(2.)  1  atom  of  A  may  unite  with  £,  1,  l£,  2,  2£,  3,  &c.,  atoms  of  B. 

But  as  an  atom  is  indivisible,  theie  can  be  no  such 
thing  as  a  half  atom ;  consequently  the  second  series  be- 
comes, 

(3.)  2  atoms  of  A  may  unite  with  1,  2,  3,  4,  5,  &c.,  atoms  of  B. 

The  three  foregoing  laws  are  known  under  the  name 
of  the  laws  of  combination ;  they  are  the  law  of  definite 
proportions,  the  law  of  numbers,  and  the  multiple  law. 

There  are  three  ways  in  which  the  composition  of  a 
substance  may  frequently  be  expressed:  1,  by  atom;  2, 
by  weight ;  3,  by  volume.  Thus,  the  constitution  of  wa- 
ter, by  atom,  is  one  of  oxygen  to  one  of  hydrogen  ;  by 
weight,  it  is  one  of  hydrogen  to  eight  of  oxygen  ;  and  by 
volume,  two  of  hydrogen  to  one  of  oxygen.  These  dif- 
ferent modes  of  expression  involve  nothing  contradictory ; 
they  are  all  reconciled  by  the  statement  that  the  atom  of 
oxygen  is  eight  times  as  heavy  as  that  of  hydrogen,  but 
only  half  the  size. 

By  some  authors  the  terms  combining  proportion  and 
equivalent  are  used ;  they  have  the  same  signification  as 
atomic  weight.  And  as  we  know  nothing  of  the  absolute 
weight  of  atoms,  but  only  their  relative  proportions  to 
each  other,  we  may  select  any  substance  with  which  to 
compare  all  the  rest,  and  make  it  our  unit  or  term  of  com- 
parison. In  this  book  hydrogen  is  employed  for  this  pur- 
pose, and  its  atomic  weight  is  marked  1 ;  on  the  Continent 
of  Europe  oxygen  is  selected,  and  marked  100.  It  is 
obvious  that  this  does  not  affect  the  relationship  of  the 
numbers,  for  it  is  the  same  thing  whether  we  state  the 
atomic  weights  of  hydrogen  and  oxygen  as  1  to  8,  or  as 
121  to  100. 

What  are  the  two  series  in  which  bodies  may  unite  ?  In  what  ways 
may  the  composition  of  a  body  be  frequently  expressed  ?  How  is  the  ap- 
parent contradiction  of  these  statements  reconciled  ?  What  do  proportion 
and  equivalent  signify!  What  is  the  substance  with  which  all  others 
are  compared  for  their  atomic  Wfigrts  in  this  book?  What  other  stand, 
ards  might  be  employed  ? 


154       SPECIFIC    GRAVITIES    AND    ATOMIC    WEIGHTS. 


Combinations  may  take  place  in  two  different  ways : 
1st,  in  definite  proportions;  2d,  in  indefinite  proportions. 
If  is  to  the  former  that  all  the  foregoing  observations  and 
laws  apply.  One  grain  of  hydrogen  will  not  unite  with 
nine  or  seven  grains  of  oxygen,  but  only  with  eight.  But 
one  drop  of  spirits  of  wine  may  combine  with  one  of  wa- 
ter, or  with  a  pint,  or  a  quart,  or  ten  gallons.  This  is 
what  is  understood  by  union  in  indefinite  proportions. 

When  two  gaseous  "bodies  unite,  their  combining  pro 
portions  bear  a  simple  relation  to  each  other  ;  one  volume 
of  hydrogen  unites  with  one  of  chlorine,  and  produces 
two  volumes  of  hydrochloric  acid.  And  in  the  case  of  the 
five  compounds  of  nitrogen  just  referred  to,  two  volumes 
of  that  gas  combine  successively  with  1,  2,  3,  4,  5  of 
oxygen. 

A  relation,  therefore,  exists  between  the  combining 
volume  and  the  atomic  weight  of  gaseous  bodies.  If  the 
weight  of  a  given  volume  of  oxygen  be  called  1000,  that 
of  an  equal  volume  of  hydrogen  will  be  625,  these  num- 
bers representing,  of  course,  the  specific  gravity  of  the 
two  gases.  The  proportion  in  which  they  unite  is  one 
volume  of  oxygen  to  two  of  hydrogen  to  form  water ;  the 
relative  weights  of  these  quantities,  therefore,  would  be 
100-0  to  6-25x2,  that  is,  lOO'O  to  12-50,  but  these  num 
bers  are  the  atomic  weights  of  the  bodies  respectively. 
From  such  considerations,  it  was  at  one  time  supposed 
that,  in  the  case  of  all  gases,  the  specific  gravities  would 
correspond  to  the  atomic  weights.  Experience  has,  how- 
ever, shown  that  this  is  not  the  case,  as  is  seen  in  the 
following  table  : 


Gas,  or  Vapor. 

Specific  Gravities. 

Chemical  Equivalents. 

Air  =  1. 

Hydrogen  =  1. 

By  Volume. 

By  Weight. 

0-0690 
0-9727" 
0.4213 
2-4700 
8-7011 
5-3930 
6-9690 
1-1025 
4-3273 
10-3620 
6-6480 

i-oo 

14-12 
6-12 
35-84 
126-30 
78-40 

101-00 

16-00 
62-8 
150-8 
96-48 

100- 
100- 
100- 
100- 

100' 

100- 
200' 
50' 
25' 
25- 
16-66 

1-00 
14-15 
6-12 
35-42 
126-30 
78-40 
202-00 
8-00 
15-70 
37-7 
16-10 

Nitrogen     

Carbon  (hypothetical)  .... 
Chlorine      .    . 

Iodine     
Bromine      

Mercury 

Oxygen      
Phosphorus     .         

Sulphur      .    .     .   '  

What  are  the  two  modes  of  combination?  What  relation  is  observed 
when  gases  combine  by  volume  ?  What  is  the  relation  between  specific 
gravities  and  atomic  weights  ? 


CALCULATION    OF    SPECIFIC    GRAVITIES.  155 

From  this  it  is  seen,  that  if  the  combining  volume  of 
hydrogen,  nitrogen,  or  chlorine  be  taken  as  unity,  that  of 
oxygen  is  one  half,  of  vapor  of  phosphorus  one  fourth,  and 
of  vapor  of  sulphur  one  sixth. 


LECTURE  XXXVI. 

CONSTITUTION  OF  BODIES. — Calculation  of  Specific  Grav- 
ities.— Crystallization. — Systems  of  Crystals. — Dimor- 
pJi ism . — Isom orphism . — IsomorpTious  Groups. — Isomer- 
ism.  —  Metameric  and  Polymeric  Bodies.  —  Allotropic 
States  of  Bodies. 

ON  the  principles  which  have  just  been  developed,  we 
can  often  calculate  the  specific  gravity  of  a  compound  gas 
with  more  accuracy  than  it  can  be  determined  experi- 
mentally. Thus,  hydrochloric  acid,  which  consists  of 
equal  volumes  of  chlorine  and  hydrogen  united,  without 
condensation,  must  have  a  specific  gravity  of  1*2695,  be- 
cause the  specific  gravity  of  hydrogen  being  0-0690,  and 
that  of  chlorine  2-4700,  the  sum  of  which,  2-5390,  is  the 
weight  of  two  volumes  of  hydrochloric  acid,  and,  there- 
fore, if  we  divide  by  2,  the  quotient,  1*2695,  is  equal  to 
the  weight  of  one  volume ;  or,  in  other  words,  the  specific 
gravity  of  the  compound  gas. 

Sometimes,  also,  we  can  determine  the  specific  gravity 
or  a  vapor  by  calculation  when  it  is  impossible  to  do  so 
experimentally.  Assuming  that  one  volume  of  carbonic 
acid  gas  contains  one  volume  of  oxygen  and  one  of  car- 
bon vapor,  we  have, 

Specific  gravity  of  carbonic  acid  .     .    .1-5238 

oxygen 1-1025 

"  carbon  vapor  .     .     .     -4213 

The  hypothetical  specific  gravity  of  the  vapor  of  carbon 
is  therefore  '4213. 

The  rule  for  the  calculation  of  specific  gravities,  on  the 
foregoing  principles,  is,  "  Multiply  the  specific  gravities 
of  the  simple  gases  or  vapors  respectively  by  the  volumes 
in  which  they  combine,  add  those  products  together,  and 

How  may  the  specific  gravity  of  a  compound  gas  be  determined  ?  How 
is  the  hypothetical  specific  gravity  of  the  vapor  of  carbon  determined  ? 
What  is  the  rule  for  the  calculation  of  the  specific  gravities  of  compound 
gases  from  those  of  their  constituents  ? 


156 


SYSTEMS    OF    CRYSTALLIZATION. 


divide  the  sum  by  the  number  of  volumes  of  the  compound 
gas  produced." 

It  frequently  happens  that  substances  assuming  the 
solid  form,  from  the  liquid  or  vaporous  states,  take  on  a 
geometrical  figure,  being  terminated  by  sharp  edges  and 
solid  angles ;  under  such  circumstances,  they  are  said  to 
crystallize.  Thus,  common  salt  will  crystallize  in  cubes, 
and  nitrate  of  potash  in  six-sided  prisms. 

The  various  geometrical  forms  which  crystals  can  thus 
assume  may  be  divided  into  six  classes,  or  systems  : 

(1.)  The  Regular  system. 

(2.\  The  Rhombohedral  system. 

(3.)  The  Square  Prismatic  system. 

(4.)  The  Right  Prismatic  system. 

(5.)  The  Oblique  Prismatic  system. 

(6.)  The  D.ou%  Oblique  Prismatic  system. 

This  division  is  founded  on  the  relations  of  certain  lines, 
or  axes,  which  may  be  supposed  to  be  drawn  through  the 
center  of  the  crystal  round  which  its  parts  are  symmetri- 
cally arranged. 

THE    REGULAR    SYSTEM. 

This  has  three  equal  axes  at  right  angles  to  each  other. 

Fig.  134. 


The  letters  a  a  show  the  direction  of  the  axes.  The 
figure  (Fig.  X34)  represents,  1.  The  cube;  2.  Regular  oc- 
tahedron ;  and,  3.  Rhombic  dodecahedron. 

THE    SQUARE    PRISMATIC    SYSTEM. 

This  has  three  axes,  two  of  which  are  equal,  and  the 
third  of  a  different  length. 

a  a  is  the  principal  axis";  I  b  the  secondary  one.  In 
the  figure  (Fig.  135),  1  is  a  right  square  prism,  with  the 
axes  on  the  center  of  the  sides,  b  b ;  2  is  a  right  square 

What  are  the  six  systems  of  crystallization  ?  Upon  what  fact  is  this 
division  founded  ?  In  the  regular  system,  what  is  the  relation  of  the  axes  1 
In  the  square  prismatic  system,  what  is  their  relation  ? 


SYSTEMS    OF  CRYSTALLIZATION. 
Fig.  135. 


157 


L 


prism,  with  the  axes  in  the  edges  ;  3  and  4  corresponding 
right  square  octahedrons. 

THE    RIGHT    PRISMATIC    SYSTEM 

has  three  axes,  a  a,  b  bt  c  c,  of  unequal  lengths,  at  right 
angles  to  each  other. 

Fig.  136. 


In  the  figure  (Fig.  136),  1  is  a  right  rectangular  prism  ; 
2.  Right  rhombic  prism  ;  3.  Right  rectangular  based  octa- 
hedron ;  4.  Right  rhombic  based  octahedron. 

THE    OBLIQUE    PRISMATIC    SYSTEM 

has  three  axes,  which  may  be  unequal ;  two  are  placed 

Fig.  137. 


What  is  it  in  the  right  prismatic  ?    In  the  oblique  and  double  obliqu* 
prismatic  systems,  what  is  it? 

o 


158 


SYSTEMS    OF    CRYSTALLIZATION. 


at  right  angles  to  each  other,  and  the  third  is  oblique  to 
one  and  perpendicular  to  the  other. 

In  the  figure  (Fig.  137),  1  is  an  oblique  rectangular 
prism;  2.  Oblique  rhombic  prism  ;  3.  Oblique  rectangular 
based  octahedron  ;  4.  Oblique  rhombic  based  octahedron. 

THE    DOUBLY    OBLIQUE    PRISMATIC    SYSTEM 

has  three  axes,  which  may  be  all  unequal  and  all  oblique. 

Fig.  138. 

a, 


in  the  figure  (Fig.  138),  1  and  2  are  doubly  oblique 
ptisms  ;  and  3  and  4  doubly  oblique  octahedrons. 

THE    RHOMBOHEDRAL    SYSTEM 

has  four  axes,  three  of  which  are  equal  in  the  same 
plane,  and  inclined  at  angles  of  60°  ;  the  fourth,  which  is 
the  principal  axis,  is  perpendicular  to  all. 

Fig.  139. 


In  the  figure  (Fig.  139),  1  is  the  regular  six-sided  prism  ; 
2,  the  dodecahedron;  3.  Rhombohedron  ;  4.  another  dode- 
cahedron. 

It  often  happens,  owing  to  a  change  in  the  deposit  of 
new  matter  on  a  crystal  while  forming,  that  other  figures 
than  the  proper  one  are  produced  ;  thus,  the  cube  may 
pass  into  the  octahedron,  as  shown  in  Fig.  140. 

How  many  axes  are  in  the  rhombohedral  system,  and  what  is  their  re- 
ation  ?  In  what  manner  may  crystals  of  one  form  pass  into  those  of 
another,  as  the  cube  into  the  octahedron  ? 


GONIOMETERS. 
Fig.  140. 


159 


The  effect  may,  perhaps,  be  better  conceived  by  imagin- 
ing the  solid  angle  of  the  cube  1  to  be  cut  off  by  planes 
equally  inclined  to  the  constituent  faces.  2  represents  an 
increased  removal  of  the  same  kind ;  3  one  still  farther 
advanced. 

Sometimes  it  happens  that  each  alternate  plane  of  a 
crystal  grows  at  the  expense  of  the  adjacent  one,  giving 
rise  to  hemihedral,  or  half-sided  crystals,  as  is  shown  in 
Fig.  141,  which  represents  the  tetrahedron,  arising  in  this 
manner  from  the  octahedron  by  the  growth  of  each  alter- 
nate face.  1.  The  octahedron  partially  modified;  2.  The 
change  farther  advanced ;  3.  The  tetrahedron  completed. 

Fig.  141. 


The  angles  of  crystals  are  measured  by  goniometers,  of 
which    there    are    several  Fig.  142. 

kinds;  as  the  common  goni- 
ometer, and  Wollaston's  re- 
flecting goniometer.  This 
instrument  is  represented 
in  Fig.  142.  The  crystal 
to  be  measured  ,yj  is  fixed 
upon  a  movable  support, 
d,  which  is  in  connection 
with  the  button  -  headed 
axis  of  the  goniometer,  o, 
which  passes  through  a  lar- 
ger axis  in  the  upright,  b. 
a  is  a  divided  circle,  and 
e  its  vernier,  which  is  fixed  immovably  on  the  upright,  b. 

What  are  hemihedral  crystals,  and  how  are  they  produced  ?     Describe 
the  use  of  the  reflecting  goniometer. 


160  DIMORPHISM. 

The  edge  of  the  crystal,  which  is  formed  by  the  two  fa- 
ces whose  inclination  is  to  be  measured,  is  to  be  set  par- 
allel to  the  axis  of  the  instrument ;  and  having,  by  means 
of  the  button,  o,  turned  the  crystal  until  some  definite  ob- 
ject, such  as  the  bar  of  a  window,  is  seen  distinctly  reflect- 
ed from  it,  the  larger  milled  head  is  turned,  and  with  it 
the  divided  circle  and  crystal,  until  the  same  object  is 
again  seen  by  reflection  from  the  second  face.  The  an- 
gle through  which  the  great  circle  has  moved,  subtracted 
from  180°,  gives  the  angle  included  between  the  two  crys- 
talline faces,  or  their  inclination  to  each  other. 

As  a  general  rule,  the  same  substance,  crystallizing  un- 
der the  same  circumstances,  will  produce  crystals  belong- 
ing to  the  same  system.  Cases,  however,  are  known  in 
which  the  same  substance  belongs  to  different  systems. 
Thus,  sulphur  will  crystallize  in  rhombic  prisms,  and  also 
rhombic  octahedrons.  By  dimorphous  bodies  we  there- 
fore mean  substances  which  will  afford  crystals  belonging 
to  two  different  systems. 

Dimorphism  is  frequently  connected  with  the  tempera- 
ture at  which  the  crystals  were  produced.  Thus,  carbon- 
ate of  lime,  at  ordinary  temperatures,  yields  rhombohe- 
drons,  but  at  the  boiling  point  of  water  right  rhombic 
prisms ;  and  with  this  difference  of  form  a  difference  of 
chemical  qualities  may  occur;  the  bisulphuret  of  iron, 
for  example,  crystallizes  in  cubes  which  remain  unacted 
upon  by  water  or  air ;  but  in  its  right  rhombic  form  it  un- 
dergoes rapid  oxydation  in  moist  air,  producing  sulphate 
of  iron.  Commonly  one  oS  the  forms  of  a  dimorphous 
body  is  less  stable  than  the  other,  and  if  the  transition 
takes  place  abruptly,  it  is  sometimes  attended  by  a  flash 
of  light. 

It  was  discovered  by  Mitcherlich,  that  when  different 
compound  bodies  assume  the  same  form,  we  are  often 
able  to  trace  a  remarkable  analogy  in  their  chemical  com- 
position. Thus,  the  chloride  of  sodium,  the  iodide  of  po- 
tassium, the  fluoride  of  calcium,  &c.,  crystallize  in  the 
first  system.  These  substances  are  all  constituted  upon 
a  common  type,  in  which  we  have  one  atom  of  a  metal 

What  is  meant  by  dimorphous  hodies  ?  What  effect  has  temperature  on 
the  formation  of  crystals  ?  Is  dimorphism  connected  with  peculiarities  in 
the  chemical  qualities  of  bodies  ?  What  relation  is  there  in  the  form  and 
composition  of  iodide  of  potassium  and  chloride  of  sodium  ? 


ISOMORPHISM.  161 

united  to  one  atom  of  an  electro-negative  radical ;  or, 
taking  M  as  the  general  symbol  for  the  metals,  and  R  for 
the  electro-negative  radicals,  the  class  is  constituted  upon 
the  type 

M,R, 

and,  therefore,  includes  such  bodies  as 

KCl ..NaCl.. KBr. . KF . .  CaF.AmCl . . . &c. 

Such  substances  are  called  isomorphous  bodies,  and  the 
designations,  isomorphous  elements,  isomorphous  groups, 
are  used,  being  derived  from  jtfoc,  equal,  /io/00?/,  form. 

Let  us  take  a  second  more  complicated  case.  The 
formula  for  common  alum,  the  sulphate  of  alumina  avid 
potash,  is, 

KO,    SO3  +  Alz  O3,  3SO3  4-  24#O. 

Ammonia  alum  is     AmO,  SO3  4-  A12  O3,  3SO3  -  -  24HO. 

Chrome  alum  is        KO,     SO3  4-  Cr2  O3,  3 SO*  -f  24/fO. 

Iron  alum  is  KO,     SO3  -f  Fez  O3,  3SO3  -f  24#O. 

And  in  the  same  way  an  extensive  family  of  alums  may 
be  formed  by  the  substitution  of  a  limited  number  of  vari- 
ous other  bodies  compiised  in  the  general  formula, 

mO,  SO3  +  M*  O3,  3SO3  +  24HO, 

in  which  m  represents  any  metal  belonging  to  the  potas- 
sium group,  and  M  any  one  belonging  to  the  aluminum 
group. 

All  these  alums  crystallize  with  the  same  form,  and 
such  illustrations  afford  us  reason  to  believe  that  that  sim- 
ilarity of  form  is  due,  in  a  great  measure,  to  the  grouping 
or  arrangement  of  the  constituent  atoms  ;  that  in  a  corn- 
pound  molecule  the  substances  which  can  replace  one  an- 
other without  giving  rise  to  a  change  of  external  form,  must 
have  certain  relationships  to  each  other.  We  call  them, 
therefore,  isomorphous.  The  following  ten  groups  have 
been  established  : 


i. 

Silver Ag 

Gold  ........     Au 

2. 

Arsenious  Acid  (in  its 
unusual  form)   .     .     .     Asz  Os 


Sesquioxide  of  Antimo- 
ny    Sh  O» 

3. 

Alumina Ah  Os 

Sesquioxide  of  Iron      .  Fez  Os 

"  Chromium  Cm  Oz 


Why  are  they  called  isomorphous  bodies  1     Give  an  example  of  iso- 
morphism in  the  case  of  the  alums.     What  general  conclusion  may  be 
drawn  from  these  facts  1     How  many  isomorphous  groups  have  been  de- 
termiued  1    Enumerate  the  members  belonging  to  each. 
O2 


162   ISOMERISM. METAMERIC  AND  POLYMERIC   BODIES 


Sesquioxide  of  Manga- 
nese          .           .      -      -      A/W.-T  Oa 

4. 
Phosphoric  Acid 
Arsenic  Acid   . 

5. 
Sulphuric  Acid 
Selenic  Acid    . 
Chromic  Acid  . 
Manganic  Acid 

.       P2   O$ 
.       S  03 

.     Se  Os 

.       003 

.    Mn  Os 

8. 

Oxide  of  Silver    .     .     . 
Oxide  of  Sodium      .     . 

9. 

Baryta 

Strontia 

Lime  (in  arragonite) 
Oxide  of  Lead 

10. 
Lime  (in  Iceland  spar) 


Hypermanganic  Acid 
Hyperchloric  Acid  . 

7. 


Mm  Or 

Cl  O7 

K.O 


Salts  of  Potash    .     .     . 
Salts  of  Oxide  of  Am- 
monium    Am  O 


Protoxide  of  Iron      .    . 

"  Manganese 

Zinc     .     . 

Cobalt       . 

Nickel      . 

Copper     . 

Lead      (in 

plumbo  calcite)    .      . 


AgO 
NaO 


BaO 
SrO 
CaO 
Pb.Q 

Ca  O 
Mg  O 
Fe  O 
Mn  O 
ZnO 
CoO 
Ni  O 
CuO 

Pb.O 


From  the  external  forms  of  bodies  we  may  next  turn 
to  their  internal  constitution,  calling  to  mind  what  has 
been  already  observed  in  Lecture  XXXIV.,  that  identity 
of  composition  by  no  means  implies  identity  of  character. 
Two  substances  may  be  composed  of  the  same  elements, 
united  in  the  same  proportions,  and  yet  be  totally  unlike ; 
and  it  is  obvious  that  this  may  be  due  to  two  different 
causes  :  1st.  Difference  of  grouping ;  2d.  Difference  in 
the  absolute  number  of  atoms. 

Difference  of  grouping  I  have  already  explained  in  the 
lecture  just  quoted  ;  and  with  respect  to  difference  in  the 
absolute  number  of  atoms,  the  effect  is  obvious  from  an 
example.  Thus,  we  have  as  the  constitution  of 

Aldehyde        .""    ,,'""  ''.        .        .        .         C^H^O2. 
Acetic  ether C8H6O^. 

And  these  bodies,  if  analyzed,  would,  of  course,  yield  pre- 
cisely the  same  proportions  in  100  parts,  the  true  differ- 
ence being ;  that  the  atom  of  acetic  ether  contains  twice 
as  many  constituent  atoms  as  that  of  aldehyde,  and  is, 
therefore,  exactly  twice  as  heavy,  though  equal  weights 
of  the  two  will  yield  equal  quantities  of  their  constituents. 
To  these  peculiarities  the  term  isomerism  is  applied, 
and  by  isomerjc  bodies  we  mean  bodies  composed  of  the 
same  elements  in  the  same  proportion,  but  differing  in 
properties.  When  isomerism  arises  from  difference  in 
grouping,  the  bodies  are  said  to  be  metameric ;  and  when 

What  two  causes  may  give  to  bodies  of  the  same  composition  different 
characters  ?  Give  an  example  of  the  effect  of  difference  of  the  absolute 
number  of  atoms.  What  is  meant  by  isomerism? 


ALLOTROPISM.  103 

it  arises  from  difference  in  the  absolute  number  of  atoms, 
they  are  called  polymeric. 

Attention  has  recently  been  drawn  to  a  third  cause, 
which  gives  rise  to  the  phenomena  of  isomerism  :  it  is  the 
allotropic  condition  of  elementary  bodies.  Carbon,  for 
example,  exists  under  a  number  of  different  forms  ;  we 
find  it  as  charcoal,  plumbago,  and  diamond.  They  differ 
in  specific  gravity,  in  specific  heat,  and  in  their  conduct- 
ing power  as  respects  caloric  and  electricity.  In  their 
relations  to  light,  the  one  perfectly  absorbs  it,  the  second 
reflects  it  like  a  metal,  the  third  transmits  it  like  glass, 
In  their  relation  to  oxygen  they  also  differ  surprisingly  ; 
there  are  varieties-  of  charcoal  that  spontaneously  take 
fire  in  the  air,  but  the  diamond  can  only  be  burned  in 
pure  oxygen  gas.  The  second  and  third  varieties  do  not 
belong  to  the  same  crystalline  form. 

It  is  now  known  that  a  great  many  elementary  substan- 
ces are  affected  in  this  manner.  I  have  shown  that  this 
is  the  case  with  chlorine  gas,  which  changes  under  the  in- 
fluence of  the  indigo  rays  (Phil.  Mag.,  July,  1844).  In 
the  same  manner,  it  has  been  long  known  that  iron  exists 
in  two  states :  1st.  In  its  ordinary  oxydizable  state ;  2d. 
In  a  condition  in  which  it  simulates  the  properties  of  pla- 
tinum or  gold. 

There  can  be  no  doubt  that  these  peculiarities  are  car- 
ried by  these  bodies  when  they  unite  to  form  compounds  ; 
thus,  for  example,  if  carbon  and  hydrogen  unite,  it  is  pos- 
sible we  may  have  three  different  compounds ;  one  con- 
taining charcoal  carbon,'a  second  plumbago  carbon,  a  third 
diamond  carbon ;  or,  if  we  designate  these  respectively  as 
Ca,  Cj3,  Oy,  we  may  have 

CaH...CpH...CyH; 

and  perhaps,  as  M.  Millon  has  suggested,  carbureted  hy- 
drogen gas  and  otto  of  roses,  which  have  the  same  con- 
stitution, differ,  in  the  one  containing  charcoal  and  the  oth- 
er diamond. 

These  peculiarities  are  known  under  the  name  of  allo- 
tropic states,  and  the  phenomenon  itself  under  the  desig- 
nation of  allotropism. 

What  are  metameric  bodies  ?  What  are  polymeric  bodies  ?  What  is 
meant  by  the  allotropic  condition  of  bodies  ?  What  allotropic  states  does 
carbon  present  ?  How  may  an  allotropic  change  be  impressed  on  chlorine  ? 
What  are  the  allotropic  states  of  iron  ?  Are  these  peculiarities  continued 
in  the  compounds  ? 


164  CHEMICAL    AFFINITY. 


LECTURE  XXXVII. 

CHEMICAL  AFFINITY. — Phenomena  accompanying  Chemi- 
cal Affinity. — Disturbance  of  Temperature. — Production 
of  Light. — Evolution  of  Electricity. — Change  of  Color. 
— Change  of  Form. — Change  of  Chemical  Properties. — 
Change  of  Volume  and  Density. —  Tables  ofGeoffroy. — 
Measure  of  Affinity. — Disturbing  Causes. 

BY  chemical  affinity  we  mean  the  attraction  of  atoms 
of  a  dissimilar  nature  for  each  other,  an  attraction  which 
is  exhibited  upon  the  apparent  contact  of  bodies. 

There  are  certain  striking  phenomena  which  very  fre- 
quently accompany  chemical  action.  They  are  the  evo 
lution  of  Light,  Heat,  and  Electricity;  and,  as  respects 
the  bodies  engaged,  they  may  exhibit  changes  of  color,  of 
form,  of  volume,  of  density,  or  of  their  chemical  proper- 
ties. 

If,  in  a  glass  vessel,  a  (Fig.  143),  a  mixture  of 
strong  sulphuric  acid  and  water  be  stirred  togeth- 
er by  means  of  a  tube,  b,  containing  some  sul- 
phuric ether,  so  much  heat  will  be  evolved  by 
the  acid  and  water  as  they  unite,  that  the  ether 
will  be  made  to  boil  rapidly. 

If,  upon  some  water  contained  in  a  shallow  dish  (Fig. 
Fig.  144.        144),  a  piece  of  potassium  be  thrown,  the 
potassium  decomposes   the  water  with  the 
evolution  of  a  beautiful  lilac  flame. 

As  respects  the  evolution  of  electricity 
during  chemical  action,  the  Voltaic  battery, 
and,  indeed,  all  Voltaic  combinations,  are  ex- 
amples. In  the  simple  circle  we  have  already,  in  Lec- 
ture XXVIII.,  traced  the  production  of  electricity  to  the 
decomposition  of  the  water. 

We  have  observed  that  the  evolution  of  the  imponder- 
able agents*is  not  the  only  phenomenon  to  be  remarked 
during  the  play  of  chemical  affinity,  the  ponderable  sub- 
stances themselves  undergo  changes. 

"What  is  meant  by  chemical  affinity  ?  What  phenomena  accompany 
chemical  action  ?  What  changes  are  exhibited  by  the  ponderable  bodies 
themselves  ?  G ive  examples  of  the  evolution  of  heat,  light,  and  electricity. 


CHANGES  OF  COLOR  AND  FORM.         105 

If,  in  a  glass  containing  litmus  water,  a  drop  of  sul- 
phuric acid  is  poured,  the  blue  color  of  the  litmus  is  at 
once  changed  to  a  red,  and  if  into  the  reddened  liquid  so 
produced  a  little  ammonia  is  poured,  the  blue  color  is 
restored.  This  simple  experiment  is  of  considerable  in- 
terest, for  the  reddening  of  litmus  is  commonly  received 
as  one  of  the  attributes  of  acid  bodies,  and  the  restoration 
of  the  blue  color  of  those  belonging  to  the  alkaline  type. 

On  adding  to  a  solution  of  sulphate  of  copper  a  small 
quantity  of  ammonia,  a  pale  green  precipitate  is  thrown 
down  ;  a  greater  quantity  of  ammonia  redissolves  this  pre- 
cipitate, and  gives  rise  to  a  splendid  purple  solution. 

A  similar  solution  of  sulphate  of  copper  gives  rise,  un- 
der the  action  of  a  solution  of  ferrocyanide  of  potassium, 
to  a  deep  chocolate-colored  precipitate. 

A  solution  of  the  nitrate  of  lead,  which  is  colorless,  act- 
ed on  by  a  solution  of  iodide  of  potassium,  also  colorless, 
gives  rise  to  the  production  of  a*beautiful  yellow  precipi- 
tate, the  iodide  of  lead. 

And,  lastly,  if  sulphuric  acid  be  placed  in  a  solution  of 
a  soluble  salt  of  lead,  or  of  baryta,  a  white  precipitate  at 
once  goes  down. 

These  are  all  instances  of  changes  of  color,  and  such 
changes  are  of  the  utmost  importance  in  practical  chem- 
istry, inasmuch  as  the  art  of  testing  depends,  for  the  most 
part,  upon  a  knowledge  of  them. 

Changes  of  form  in  the  same  manner  are  exhibited  ; 
thus,  when  gunpowder  explodes,  a  large  proportion  of  the 
ingredients,  from  being  in  the  solid,  escapes  in  the  gaseous 
state.  If,  upon  fragments  of  chalk,  carbonate  of  lime,  we 
pour  hydrochloric  acid,  a  violent  effervescence  takes  place, 
due  to  the  escape  of  carbonic  acid,  which,  from  being  in 
the  solid,  assumes  the  gaseous  form. 

The  converse  of  this  is  sometimes  seen,  va- 
pors  passing  into  the  solid  state.  In  the  glass, 
a  (Fig.  145),  place  some  strong  hydrochloric 
acid,  and  in  b  some  strong  ammonia ;  both  these 
bodies  yield  vapors  at  ordinary  temperatures  in 
abundance,  and  those  vapors  meeting  in  the  air 
over  the  glasses,  give  rise  to  a  dense  fume,  or  smoke, 
which,  if  examined,  proves  to  be  solid  sal  ammoniac. 

Give  examples  of  changes  of  color.  On  what  do  the  processes  of 
testing  for  the  most  part  depend  ?  Give  an  example  of  the  production  of 
a  gas  from  a  solid,  and  a  solid  from  gases. 


1G6 


CHANGES    OF    PROPERTIES. 


146. 


Very  often  change  of  form  is  accompanied 
by  change  of  color  ;  thus,  if  under  a  large  bell 
jar  (Fig.  146)  there  be  placed  a  wine-glass 
containing  a  few  copper  or  iron  nails  and  nitric 
acid,  a  gas  of  a  deep  orange  color  makes  its 
appearance,  filling  the  whole  bell. 

Perhaps  no  better  instance  of  an  entire 
change  of  properties  could  be  cited  than  that  of  the  com- 
bustion of  phosphorus  in  atmospheric  air.  This  substance 
Fig.  147.  phosphorus  is  a  body  of  a  waxy  appear- 
ance, possessing  so  great  a  degree  of  com- 
bustibility that  it  requires  to  be  kept  un- 
der the  surface  of  water  to  prevent  the  ac- 
tion of  the  air.  If  a  piece  of  it  be  set  on 
fire  beneath  a  clear  and  dry  bell  jar,  as 
shown  in  Fig.  147  >  it  unites  with  great 
energy  with  the  oxygen  of  the  included 
air,  producing  white  flakes,  which,  as  the 
combustion  is  ceasing,  descend  in  the  jar,  giving  a  min- 
iature representation  of  a  fall  of  snow.  On  collecting  some 
of  this  phosphoric  snow,  its  properties  will  be  found  to  be 
in  striking  contrast  with  the  phosphorus  which  produced 
it  ;  for  instance,  far  from  being  unacted  on  by  water,  it 
has  such  an  intense  affinity  for  that  substance,  that  it 
hisses  like  a  red-hot  iron  when  brought  in  contact  with 
it.  It  reddens  litmus  solution,  and  possesses  the  quali- 
ties of  a  powerful  acid.  Nor  is  the  change  confined  to 
the  phosphorus  ;  if  we  examine  the  air  in  which  it  was 
burned,  we  find  it  has  lost  its  quality  of  supporting  com- 
bustion. 

Changes  of  volume,  and,  consequently,  changes  of  dens- 
ity, constantly  attend  chemical  action  ;  a  pint  of  water  and 
a  pint  of  sulphuric  acid,  mixed  together,  form  less  than 
two  pints  ;  and  the  same  may  be  observed  of  alcohol  and 
water. 

When  to  two  substances  already  in  union,  a  third,  hav- 
ing a  stronger  affinity  for  one  of  the  other  two,  is  present- 
ed, decomposition  ensues-  Thus,  if  to  the  carbonate  cf 
soda  nitric  acid  be  presented,  the  soda  and  nitric  acid  com- 
bine, and  the  carbonic  acid  is  driven  off  in  the  form  of  a 


What  are  the  changes  which  phosphorus  undergoes  when  burned  in 
the  air?  Give  an  example  of  change  of  volume  and  of  density  Under 
what  circumstances  does  decomposition  take  place 1 


MEASURE    OF    CHEMICAL    AFFINITY.  167 

gas.  And,  again,  if  upon  the  nitrate  of  soda  so  produced 
sulphuric  acid  is  poured,  the  nitric  acid  is  driven  off,  and 
sulphate  of  soda  results.  It  was  at  one  time  thought  that, 
by  examining  a  number  of  such  cases,  we  might  discover 
the  order  of  affinity  of  bodies  for  one  another  and  arrange 
them  in  tables ;  these  are  sometimes  called  the  Tables  of 
Geoffroy.  Thus,  the  table 


Soda. 


Sulphuric  acid, 

Nitric  *»•'.' 

Muriatic       " 

Acetic          " 

Carbonic      " 

presents  us  with  the  order  in  which  a  number  of  acids 
stand  in  relation  to  soda,  the  most  powerful  being  the  first 
on  the  list,  and  the  salt  which  results  from  the  union  of 
any  one  of  those  acids  with  the  soda  can  be  decomposed 
by  the  use  of  any  other  acid  standing  higher  on  the  list.  . 
But  it  is  now  known  that  these  tables  are  far  from  rep- 
resenting the  order  of  affinities ;  a  weaker  affinity  often 
overcomes  a  stronger  by  reason  of  the  intervention  of 
disturbing  extraneous  causes  ;  and  tables  so  constructed 
lead,  therefore,  to  contradictory  conclusions.  Some  very 
simple  considerations  may  illustrate  this.  Potassium  can 
take  oxygen  from  carbon  at  low  temperatures,  or,  in  other 
words,  decompose  carbonic  acid  gas,  but  it  by  no  means 
follows  that  the  affinity  of  potassium  for  oxygen  is  great- 
er than  that  of  carbon,  and  accordingly  we  find  that  at 
higher  temperatures  carbon  can  take  oxygen  from  potas- 
sium. Indeed,  under  the  influence  of  heat,  light,  and 
electricity,  we  find  all  kinds  of  chemical  changes  going 
on,  and  in  the  same  manner  the  condition  of  form  exerts 
a  remarkable  influence  in  these  respects,  so  that  cohesion 
and  elasticity  may  be  placed  among  the  predisposing  caus- 
es producing  chemical  results.  If  a  number  of  bodies 
6xist  in  a  solution  together,  they  will  at  once  arrange 
themselves  hi  such  a  way  under  the  influence  of  cohesion 
as  to  produce  insoluble  precipitates,  if  that  be  possible  ; 
or,  under  the  influence  of  elasticity,  to  determine  the  evo- 

What  are  the  tables  of  Geoffrey  ?  How  may  it  be  shown  that  these 
are  not  tables  of  affinity  ?  What  may  be  enumerated  among  these  dis- 
turbing causes  ?  What  is  the  influence  of  cohesion  ?  What  is  the  influ- 
ence of  elasticity  ?  Give  examples  of  the  action  of  the?-Q  disturbing  agents 


168  TABLES    OF    GEOFFROY. 

lution  of  a  gas ;  if  the  carbonate  of  soda  is  decomposed 
by  acetic  acid,  it  by  no  means  follows  that  the  latter  has 
the  stronger  affinity  for  soda,  the  decomposition  being 
probably  determined  by  the  fact  that  the  carbonic  acid 
can  take  on  the  elastic  form  and  escape  away  as  a  gas. 
The  sulphate  of  soda  may  be  decomposed  by  baryta,  the 
cause  of  the  decomposition  being  probably  due  to  cohe- 
sion, for  the  sulphate  of  baryta  which  results  is  a  very  in- 
Boluble  body.  We  have,  therefore,  no  true  measure  of 
affinity,  for  the  relation  of  bodies  in  this  respect  changes 
with  external  conditions,  and  the  tables  of  Geoffroy  are 
only  tables  of  the  order  of  decompositions,  but  not  of  the 
order  of  affinity. 

What  do  the  tables  of  Geoffroy,  in  reality,  express  ? 


PART  III, 

INORGANIC    CHEMISTRY, 


LECTURE  XXXVIII. 

PNEUMATIC  CHEMISTRY. — Ancient  Opinions  on  the  Con- 
stitution of  the  Gases. — Doctrine  of  the  Unity  of  Air. 

OXYGEN  GAS. — Modes  of  Preparation. — Properties. — Ori- 
gin of  its  Name. —  Relations  to  Atmospheric  Air  and 
Combustion.- — Burning  of  Metals. 

IN  the  catalogue  of  the  elementary  bodies  of  the  an- 
cients four  substances  were  included,  earth,  air,  fire,  and 
water.  The  progress  of  knowledge  has  shown  that  three 
out  of  the  four  are  compound  bodies. 

For  a  length  of  time  it  was  supposed  that  the  various 
exhalations  and  vapors  were  nothing  more  than  vitiated 
forms  of  atmospheric  air ;  and  though  from  time  to  time 
first  one  and  then  another  of  the  gaseous  bodies  was  dis- 
covered, chemists  were  slow  to  admit  that  they  were  any 
thing  more  than  modifications  of  one  common  principle. 
Thus,  Roger  Bacon,  in  the  thirteenth  century,  discovered 
one  of  the  carburets  of  hydrogen,  and  Van  Helmont,  in 
the  sixteenth,  carbonic  acid.  The  invisibility  of  these 
bodies,  their  remarkable  chemical  relations  in  extinguish- 
ing flame  and  producing  death,  the  great  mechanical  force 
to  which  they  often  gave  rise  when  generated  in  pent-up 
vessels,  their  occurrence  in  mines,  the  bottom  of  wells,  in 
church-yards,  and  lonely  places,  suggested  to  a  supersti- 
tious mind  a  supernatural  origin,  and  Van  Helmont  gave 
them  the  name  of  gas,  corrupted  from  gahst  (or  geist), 
which  signifies  a  ghost  or  spirit. 

But  it  is  to  the  researches  on  the  properties  of  fixed  air, 
which  Black  made  about  1750,  that  pneumatic  chemistry 
owes  its  origin.  These  were  soon  followed  by  the  dis- 
coveries of  Priestley,  Scheele,  and  others.  That  of  oxygen 

"What  opinions  were  formerly  held  respecting  the  different  gases  ? 
What  was  the  original  signification  of  the  terra  gas  ?  By  whom  was  tho 
doctrine  of  the  plurality  of  airs  established  ? 

P 


170 


PREPARATION    OF    OXYGEN. 


gas,  by  the  former  of  these  philosophers,  in  1784,  forever 
destroyed  the  ancient  notion  of  vitiated  airs  ;  for  this  gas 
can  support  combustion  arid  respiration  far  better  than  the 
atmosphere.  It  may  be  said  with  justice  that  modern 
chemistry  dates  its  origin  from  the  discovery  of  oxygen  gas. 

OXYGEN.     O  =  8-013. 

Oxygen  gas  is  probably  the  most  abundant  of  the  ele- 
ments. It  constitutes  about  one  third  of  the  weight  of  the 
solid  mass  of  the  earth,  eight  ninths  of  that  of  the  waters 
of  the  sea,  and  one  fifth  the  volume  of  the  air. 

A  simple  mode  of  preparing  oxygen  is  to  place  in  a  re 


tort,  a,  Fig.  148,  some  red  oxide  of  mercury,  connecting 
with  the  retort  a  receiver,  b,  from  which  there  passes  a 
bent  tube,  c,  which  dips  beneath  the  water  of  a  pneumatic 
trough,  g.  On  raising  the  temperature  of  the  oxide  by 
the  flame  of  a  spirit  lamp,  it  is  resolved  into  metallic  mer- 
cury and  oxygen  gas ;  the  former  distills  into  the  receiver  b, 
and  the  latter  collects  in  the  inverted  jar  of  the  trough. 

Another  process  is  to  place  the  peroxide  of  manganese 
(Mn.  O2)  in  an  iron  bottle,  from  which  a  tube,  b,  Fig.  149, 
projects;  this  tube  may  be  connected  with  another,  f,  by 
means  of  a  cork  and  an  India-rubber  tube,  e.  The  bot- 
tle is  to  be  arranged  in  a  small  furnace,  and  made  red  hot; 
the  manganese  loses  one  third  of  its  oxygen,  which  may 
be  collected  in  a  gas-holder,  as  shown  in  the  figure. 

The  most  convenient  mode  of  preparing  it  is  to  place  in 
a  flask,  a,  Fig.  150,  a  mixture  of  chlorate  of  potash  and 
peroxide  of  manganese ;  to  the  mouth  of  the  flask  a  tube, 
ft,  is  adapted  by  means  of  a  tight  cork,  the  lower  end  of  the 

In  what  bodies  does  oxygen  occur  ?     Describe  its  preparation  from  red 
oxide  of  mercury,  from  peroxide  of  manganese,  and  from  chlorate  of  potash. 


PREPARATION    OP    OXYGEN. 


171 


Fig.  149. 


tube  dipping  beneath  a  jar  upon  Fig.iso. 

the  pneumatic  trough,  c.     On  rais- 

ing the  temperature  of  the  flask  by 

a  spirit  lamp,  oxygen  gas  is  freely 

evolved.     The  peroxide  of  manga- 

nese takes  no  part  in  the  change, 

out  it  causes  the  decomposition  to 

go  on  at  a  low  temperature,  and  the  gas  is  more  rapidly 

set  free.     The  change,  being  confined  to  the  chlorate  of 

potash,  is  therefore  expressed  as  follows  : 


that  is,  the  chlorate  of  potash,  at  the  temperature  in  ques- 
tion, has  its  atoms  disarranged,  resolving  itself  into  ona 
atom  of  chloride  of  potassium  and  six  atoms  of  oxygen  gas. 

It  may  also  be  prepared  by  exposing  a  mixture  of  bi 
chromate  of  potash  and  sulphuric  acid,  or  peroxide  of 
manganese  and  sulphuric  acid,  to  heat. 

Oxygen  gas  is  a  colorless  body,  having  no  odor  no\ 
taste.  It  is  a  non-conductor  of  electricity,  and  a  bad  re 
fractor  of  light.  It  is  a  powerfully  electro-negative  ele- 
ment. In  specific  gravity  it  is  heavier  than  atmospheric 
air;  for  the  air  being  1*000,  oxygen  is  1*1026,  or,  accord- 
ing to  some  chemists,  I'll  11.  One  hundred  cubic  inches 
weigh  about  34  grains.  Its  atomic  weight,  is  8*013,  hy- 

What  are  its  leading  physical  properties  ?    What  is  its  specific  gravity  ? 


172  PROPERTIES    OF    O 

drogen  being  taken  as  I'OOO.     It  has  never  been  con- 
densed into  the  liquid  state. 

To  a  certain  extent  it  is  soluble  in  water,  one  hundred 
volumes  of  that  liquid  dissolving  about  four  of  the  gas,  a 
fact  of  considerable  importance  in  physiology,  as  it  is  upon 
the  oxygen  so  found  in  water  that  aquatic  animals  depend 
for  their  respiratory  process. 

On  litmus  water,  or  any  blue  vegetable  solution,  oxy- 
Fig.  151.  gen  exerts  no  action,  as  is  easily  shown  by  agita- 
ting it  with  such  a  solution  in  Hope's  eudiometer 
(Fig.  151) ;  but  though  it  is  not  acid  itself,  when 
it  unites  with  a  great  variety  of  bodies  it  gives 
rise  to  powerful  acids,  and  from  this  circumstance 
its  name  was  derived.  Oxygen,  o%v$,  acid,  and 
yevveLv,  to  generate. 

The  most  important  qualities  of  atmospheric  air 
are  due  to  the  presence  of  oxygen  gas.  It  is  for  this  reas- 
on that  the  air  supports  combustion  and  respiration.  The 
powers  of  oxygen,  in  this  respect,  may  be  illustrated  by 
many  striking  experiments  ;  thus,  if  into  a  jar  filled  with 
Fig.  152.  it,  a  stick  of  wood,  with  a  spark  of  fire  on  its  ex- 
tremity, be  immersed,  it  bursts  out  at  once  into  a 
flame,  burning  brilliantly. 

On  immersing  a  lighted  taper  in  a  jar  of  oxygen 
(Fig.  152),  the  light  becomes  of  a  dazzling  white- 
ness, the  taper  wasting  rapidly  away ;  but  it  is  to 
be  observed  that  after  a  time  the  combustion  de- 
clines, and  finally  the  light  is  extinguished. 
If  a  piece  of  charcoal  of  bark  in  an  ignited  state  be 
placed  in  a  bottle  of  oxygen,  the  combustion 
goes  on  with  great  activity,  a  multitude  of 
sparks  being  thrown  off.  When  the  char- 
coal is  extinguished,  if  a  little  lime-water  be 
poured  into  the  bottle  and  agitated  in  it,  the 
lime-water  at  once  becomes  of  a  milky  white- 
ness ;  for  the  carbon,  during  the  combustion,  uniting  with 
the  oxygen,  produces  carbonic  acid  gas,  and  this  forms 
with  lime  a  white  insoluble  precipitate,  the  carbonate  of 
lime. 

Can  it  be  liquefied  ?  Is  it  soluble  in  water  ?  From  what  circumstance 
is  its  name  derived  ?  What  are  its  relations  in  the  ordinary  processes  of 
combustion  ?  Describe  its  effect  on  a  liehted  taper,  and  on  isrnited  char- 
coal. 


COMBUSTION    IN    OXYGEN. 


173 


A  piece  of  India-rubber  set  on  fire,  and  immersed  in 
oxygen  gas,  burns  with  the  emission  of  a  daz-       Fig.  154. 
zling  light.     And  if,  upon  a  small  stand,  some 
burning  sulphur  is  placed,  and  a  jar  of  oxygen 
inverted  over  it,  as  shown  in  Fig.  154,  the 
light  which  is  emitted  is  of  a  splendid  blue 
color,  and  the  smoke  ascending  up  the  middle 
of  the  jar,  and  falling  in  curious  rings  down 
its  sides,  affords  an  illustration  of  the  manner 
in  which  currents  are  excited  in  gases. 

But  it   is  not  alone  such   substances   as  wood,  char- 
coal, or  sulphur  which  will  burn  in  oxygen  gas  ;   Fig.  155. 
many  bodies  commonly  regarded  as  incombustible 
give  rise  to  the  same  result.     If  a  piece  of  steel 
wire  be  rolled  round  into  a  spiral,  and  the  ex- 
tremity of  it  be  dipped  in  melted  sulphur,  or 
wrapped  round  with  cotton,  so  as  to  afford  the 
means  of  introducing   it  in  an  ignited  condition 
Fig.  156.  into  oxygen  gas,  the 

combustion  is  at  once  commu- 
nicated to  the  steel,  which 
burns  in  a  very  brilliant  man- 
ner, emitting  scintillations. 

A  stream  of  oxygen  from  a 
gas-holder,  being  thrown  upoiv 
an  iron  nail  made  red  hot  in 
the  flame  of  a  spirit  lamp,  or 
placed  in  an  ignited  cavity  in 
a  piece  of  charcoal,  causes  the 
iron  to  burn  with  rapidity, 
emitting  a  shower  of  sparks. 

What  is  its  effect  on  ignited  sulphur  ?    What  is  its  effect  on  an  ignited 
metal,  as  iron  or  steel  ? 

P2 


174  COMBUSTION    IN    OXYGEN. 


LECTURE    XXXIX. 

OXYGEN  CONTINUED. — Drummond's  Light. — Combustion  of 
Phosphorus. — Double  Change  arising  in  Combustion. — 
The  Lavoisierian  Doctrine.  —  Basic,  Indifferent,  and 
Acid  Oxides. — Physiological  Relations  of  Oxygen. — 
Supporters  of  Combustion. — Nature  of  Flame. —  Con- 
stancy of  Heat  evolved. —  Vegetable  Origin  of  Oxygen 
in  the  Air. 

IF  a  piece  of  lime  the  size  of  a  peppercorn  be  placed 
in  the  flame  of  a  spirit  lamp,  through  which  oxygen  gas 
is  directed  by  a  blowpipe,  the  lime  phosphoresces  pow- 
erfully, emitting  a  light  so  bright  that  the  eye  can  scarcely 
bear  it.  This  is  the  original  form  of  what  is  called  Drum- 
mond's light.  The  light,  however,  is  still  brighter  when 
the  oxyhydrogen  blowpipe  is  employed. 

Fie-.  157.  '•^^e  combustion  of  phosphorus  in  oxy- 

gen gas  constitutes  one  of  the  most  brill- 
iant experiments.  A  piece  of  lighted  phos- 
phorus immersed  in  an  atmosphere  of  this 
gas,  burns  with  the  evolution  of  a  prodig- 
ious amount  of  light  and  heat,  Fig.  157. 
Notwithstanding  the  production  of  dense 
flakes  of  phosphoric  acid  intervening  be- 
tween the  eye  and  the  burning  mass,  the 
light  is  very  brilliant. 

When  any  combustible  substance  is  burned  in  oxygen 
gas,  two  striking  phenomena  are  exhibited  :  a  change  in 
the  combustible,  and  a  change Ifethe  oxygen.  A  fragment 
of  ignited  charcoal  rapidly  wastes  away,  and  the  surround- 
ing gas  loses  its  power  of  supporting  combustion.  Until 
the  time  of  Lavoisier,  it  was  generally  supposed  that  burn- 
ing was  due  to  the  escape  of  a  certain  principle,  called 
phlogiston,  from  bodies,  but  he  showed  that  in  all  these 
cases  there  is  no  loss  of  weight,  and  that,  in  reality,  the 

What  is  the  original  form  of  the  Drummond  light  ?  What  are  the  phe- 
nomena of  the  combustion  of  phosphorus  in  oxygen  ?  In  these  combus- 
tions, what  changes  take  place  in  the  oxygen  and  in  the  burning  body  ? 


THE    OXIDES.  175 

combustion  is  due  to  the  oxygen  uniting  with  the  burning 
body ;  and  if  care  be  taken  to  collect  all  the  products  of 
the  action,  their  united  weight  will  be  exactly  that  of  the 
oxygen  and  combustible  conjointly.  Lavoisier  was  dis- 
posed to  believe,  that  in  all  cases  of  true  burning  the  pres- 
ence of  oxygen  is  indispensable,  an  idea  now  known  to 
be  erroneous ;  for  light  and  heat  are  evolved  in  all  cases 
where  chemical  action  is  going  on  with  great  intensity, 
no  matter  what  may  be  the  substances  which  happen  to 
be  present. 

In  the  Lavoisierian  system  of  chemistry,  oxygen  was 
regarded  as  being  the  essential  supporter  of  combustion  ; 
and  as,  in  many  instances,  it  gives  rise  to  the  production 
of  acids,  it  was  also  regarded  as  the  essential  principle  of 
acidity ;  and  from  this  circumstance  its  name  was  derived, 
as  has  been  already  said.  But  so  far  from  every  acid 
containing  oxygen  gas,  it  is  now  well  known  that  there 
are  many  from  which  this  principle  is  wholly  absent.  If 
any  substance  in  particular  deserves  the  name  of "  the 
acid  former,"  it  is  hydrogen,  for  it  is  doubtful  whether 
any  powerful  acid  exists  which  does  not  contain  hydro- 
gen. Basic  substances,  on  the  contrary,  are  characterized 
by  containing  oxygen. 

To  the  compounds  which  arise  from  the  unien  of  oxy- 
gen with  other  bodies  the  generic  designation  of  oxides 
is  given  ;  and  of  them  we  have  three  classes.  1st.  Basic 
oxides.  2d.  Indifferent  oxides.  3d.  Acids.  If  M  repre- 
sents an  electro-positive  body,  the  basic  oxides  are  con- 
stituted as  follows : 

MO      .  .  .  Protoxide,  usually  the  most  powerful  base. 

Mz  03  .  .  •  Sesquioxide,  a  weaker  base. 

MO,    .  .  Deutoxide,  a  still  weaker  base. 

M20    .  .  .  Suboxide, 

The  oxides  of  manganese  furnish  a  good  example  of 
the  three  classes : 

Protoxide  of  manganese 
Sesquioxide 
Deutoxide  . 
Manganic  acid    . 
Hypermanganic  acid  . 

What  was  Lavoisier's  theory  of  combustion?  What  is  the  relation  of 
oxygen  to  acid  and  basic  bodies  ?  What  is  the  generic  designation  for  its 
compounds  ?  What  are  the  three  classes  of  compounds  which  it  yields  ? 
In  the  basic,  the  indifferent,  and  the  acid  group,  what  is  the  general  rela- 
tion of  the  ox  vaen  ? 


MnOt      Indifferent  oxide. 


176  PHYSIOLOGICAL   RELATIONS    OF    OXYGEN. 

From  which  it  may  be  inferred  that,  in  a  family  of  ox- 
ides of  an  electro-positive  body,  the  most  powerful  base  i» 
that  containing  one  atom  of  oxygen,  and  that,  as  the  quaa- 
tity  of  this  element  increases,  indifferent  bodies  may  be 
formed  ;  that  is  to  say,  those  in  which  neither  the  basic 
nor  acid  qualities  are  well  marked,  and  on  a  still  farther 
increase  acids  are  produced.  In  this  respect,  therefore, 
the  original  idea  of  Lavoisier  respecting  the  character  of 
oxygen  is  to  some  extent  substantiated. 

In  its  physiological  relations  oxygen  is  a  most  interest- 
ing body.  It  is  for  the  purpose  of  introducing  this  ele- 
ment to  the  interior  of  the  system  that  the  respiratory 
mechanism  of  animals  is  devoted — a  mechanism  which 
differs  according  to  their  mode  of  life,  the  gills  of  a  fish 
and  the  lungs  of  a  man  having  the  same  ulterior  object. 
If  two  jars  are  taken,  one  full  of  atmospheric  air,  and  one 
of  oxygen  gas,  and  small  animals  placed  beneath  each,  it 
will  be  found  that  in  the  latter  those  animals  survive 
much  longer  than  in  the  former.  The  gas  introduced 
into  the  system  arterializes  the  blood,  and,  eventually  unit- 
ing with  carbon  and  hydrogen,  keeps  up  the  temperature 
to  a  standard  point,  which,  in  the  human  mechanism,  is 
about  98°  F.  Oxygen  gas,  therefore,  is  emphatically  the 
supporter  pf  respiration. 

The  terms,  supporter  of  combustion  and  combustible 
body,  formerly  much  used  by  chemical  writers,  are  ex- 
pressive of  an  erroneous  idea.  No  substance  is  in  itself 
a  supporter  of  combustion,  nor  is  any  one  intrinsically  a 
combustible  body.  If  a  jet  of  hydrogen  burns  in  an  at- 
mosphere of  oxygen,  so,  also,  will  a  jet  of  oxygen  burn  in 
an  atmosphere  of  hydrogen  gas.  In  fact,  both  bodies  are 
equally  engaged  in  producing  the  result,  combustion  only 
taking  place  upon  their  mutual  surface  of  contact.  Th* 
division  in  question  has  arisen  from  the  circumstance  that 
the  most  familiar  instances  of  combustion  we  witnesf 
take  place  in  the  atmosphere,  which  owes  all  its  active 
qualities  to  the  presence  of  oxygen. 

Combustion  takes  place  only  at  those  points  where  th* 
uniting  substances  are  in  contact.  The  flame  of  a  can- 

For  what  purpose  is  oxygen  introduced  into  the  system  ?  Why  is  it  to 
be  regarded  as  the  supporter  of  respiration  ?  Is  the  division  of  bodies  inet 
combustibles  and  supporters  of  combustion  a  correct  one  ?  What  i 
nature  of  flame? 


STRUCTURE    OF    FLAME.  177 

die  is  not  incandescent  throughout,  but  is  a  Fig.  158. 
mere  superficies  or  luminous  shell,  with  a  dark 
interior.  In  such  a  flame  several  distinct  parts 
may  be  traced.  Around  the  wick,  a,  Fig.  158, 
at  the  points  i  i,  the  light  is  of  a  blue  color ;  for 
here  the  air  being  in  excess,  the  combustion  is 
perfect.  From  this  toward  c  the  combustible 
matter  predominates,  and  the  light  is  most  in- 
tense. A  faint  exterior  cone,  e  e,  surrounds  the 
more  luminous  portion,  but  the  interior  at  b  is 
totally  dark,  as  may  be  proved  by  placing  a 
piece  of  mica  or  glass  upon  the  flame.  It  is  prob- 
able that  the  light  arises  chiefly  from  the  ignition  of  solid 
matter,  for  incandescent  gases  are  only  faintly  luminous. 
The  hydrogen  of  the  flame  is  first  burned,  and  for  a  mo- 
ment carbon  is  set  free  in  the  solid  form  at  a  very  high 
temperature,  its  oxydation  instantly  ensuing. 

A  given  weight  of  a  combustible  body,  when  burned,  will 
always  furnish  a  constant  amount  of  heat.  If  an  ounce  of 
carbon  be  burned  in  a  few  moments  in  pure  oxygen  gas, 
the  amount  of  heat  disengaged  appears  to  be  very  great ; 
though,  in  reality,  it  is  the  same  that  would  finally  be  yield- 
ed by  a  slower  combustion  in  atmospheric  air.  So,  too,  me- 
tallic iron  becomes  white  hot  when  burned  in  oxygen,  be- 
cause the  combination  goes  forward  with  great  rapidity ; 
but  precisely  the  same  amount  would  be  yielded  in  the  slow 
oxydation  of  rusting,  though  in  the  latter  instance  it  might 
take  years  for  the  completion  of  the  process.  This  is  a 
fact  of  great  physiological  importance. 

We  have  just  said  that  atmospheric  air  owes  all  its  ac- 
tivity to  the  presence  of  oxygen,  and  as  there  are  inces- 
santly combustive  processes  going  on,  the  tendency  of 
which  is  to  remove  oxygen  from  the  air  and  generally  re- 
place it  with  carbonic  acid — a  result,  also,  which  ensues 
from  respiration,  in  every  part  of  the  earth  where  animals 
are  found — it  would  appear  a  necessary  consequence  that 
the  constitution  of  the  air  should  incessantly  change,  the 
amount  of  oxygen  declining  and  that  of  carbonic  acid  in 
creasing.  But  in  this  respect  the  vegetable  world  exerts 

Why  do  the  different  regions  of  a  lamp  flame  differ  in  luminous  power? 
Is  there  any  difference  in  the  amount  of  heat  evolved  in  rapid  and  in  slow 
combustions  ?  What  are  the  causes  which  tend  to  diminish  the  amount 
of  oxygen  in  the  air  ? 


178  ORIGIN    OF    OXYGEN    IN    NATURE. 

an  opposite  tendency  to  the  animal ;  for,  under  the  influ 
ence  of  the  light  of  the  sun,  plants  decompose  carbonic 
acid  gas,  setting  free  its  oxygen,  and  appropriating  the 
carbon  to  their  own  uses.  This  beautiful  fact  was  origin- 
ally discovei  ed  by  Priestley,  who  found,  that  if  some  green 
Fig.  159.  leaves  were  placed  in  a  bottle,  as  in  Fig.  159,  con- 
taining carbonic  acid  gas,  or,  what  is  more  conven- 
ient, water  holding  that  substance  in  solution,  so 
long  as  the  sun  does  not  shine  on  them  no  action  is 
perceived  ;  but  if  the  bottle  be  set  in  the  sun,  bub- 
bles of  gas  are  rapidly  disengaged  from  the  leaves, 
and,  rising  up  through  the  water,  collect  in  the  upper 
part  of  the  bottle,  and,  if  examined,  prove  to  be  very  rich 
in  oxygen. 

A  question  has  arisen  as  to  what  principle  the  remark- 
able decomposition  is  due.  I  have  proved,  by  causing  it 
to  take  place  in  the  prismatic  spectrum,  that  it  is  due  to 
the  yellow  ray  of  light. — (Phil.  Mag.,  Sept.,  1843.) 


LECTURE  XL. 

HYDROGEN.  —  Preparation  and  Properties  of  Hydrogen.  — 
Relations  to  Respiration.  —  Combustibility  .—Its  Light- 
ness. —  Explosive  Combustion.  —  Production  of  Water.— 
Oxyhydrogen  Blow-pipe. 

HYDROGEN.    #"=]. 

IF  a  piece  of  potassium  be  wrapped  in  paper  and  rap- 
idly immersed  beneath  an  inverted  jar  at  the  water-trough, 
violent  reaction  soon  sets  in,  a  gas  collects  in  the  upper 
part  of  the  jar,  and  the  potassium,  oxydizing,  dissolves  in 
the  water.  The  gas  so  produced  is  hydrogen,  and  the 
decomposition  is  very  simple,  as  shown  in  the  following 
symbols  : 


that  is,  water  acted  upon  by  metallic  potassium  yields  ox- 
ide of  potassium  and  hydrogen  gas. 

In  practice  more  economical  processes  are  resorted  to. 
Like  potassium,  metallic  zinc  can  decompose  water.  at  or- 
dinary temperatures,  but  there  is  this  difference  between 

By  what  agency  is  this  tendency  compensated  ?    What  is  the  principle 
of  the  decomposition  of  water  by  potassium  ? 


HYDROGEN    GAS.  179 

them,  that  while  the  oxide  of  potassium  is  very  soluble  in 
water,  the  oxide  of  zinc  is  nearly  insoluble.  A  plate  of 
polished  zinc  immersed  in  water  does  not,  therefore,  give 
rise  to  a  stream  of  gas,  for  the  moment  the  incipient  ac- 
tion has  set  in  it  ceases,  the  zinc  becoming  covered  with 
an  impervious  pellicle  of  oxide,  which  cuts  off  farther 
contact  with  the  water. 

If,  however,  we  add  any  acid  substance  which  can  form 
with  the  oxide  a  salt  soluble  in  water,  the  action  will  go 
on  continuously,  because  the  zinc  can  now  expose  a  clear 
metallic  contact.  Such  a  substance  is  sulphuric  acid.  To 
make  hydrogen,  therefore,  we  take  a  bottle,  Fig.  160. 
a,  Fig.  160,  and  having  placed  in  it  some 
strips  of  zinc,  add  sufficient  water  to  cover 
them  entirely,  and  then  adjust  to  the  mouth 
of  the  bottle  a  cork,  through  which  two  tubes, 
b  and  c,  pass.  Through  b  sulphuric  acid  is 
poured  in  such  a  quantity  as  to  excite  a  brisk 
but  not  too  violent  effervescence,  and  the  gas, 
as  it  generates,  passes  out  through  c.  It  is  absolutely  nec- 
essary'to  allow  a  quantity  of  the  gas  to  escape  before  at- 
tempting to  collect  it,  because  the  first  portions  form,  with 
the  air  in  the.  upper  part  of  the  bottle,  an  explosive  mix- 
ture ;  but  as  soon  as  it  is  judged  that  the  air  is  all  expelled, 
we  may  proceed  to  collect  the  gas ;  and  whenever  the  pro- 
duction slackens,  if  more  acid  be  added  through  the  fun- 
nel tube,  b,  the  supply  may  be  kept  up. 

Hydrogen  gas  is  a  transparent  and  colorless  body, 
which  exerts  a  powerful  refracting  action  on  light.  When 
pure,  it  has  neither  taste  nor  smell,  but,  as  thus  obtained, 
it  has  a  peculiar  odor.  It  is  the  lightest  body  in  nature,  its 
specific  gravity  being  0-0694.  One  hundred  cubic  inches 
of  it  weigh  2'1  grains.  The  weight  of  its  atom  is  taken 
as  the  standard  of  comparison  of  other  atomic  weights  in 
this  book;  it  is  therefore  =  1.  It  exerts  no  action  on 
vegetable  colors,  and  is  very  sparingly  soluble  in  water, 
one  hundred  cubic  inches  of  that  liquid  dissolving  about 
one  and  a  half  of  hydrogen  gas.  Hydrogen  has  never 
been  liquefied. 

As  respects  the  animal  economy,  hydrogen  gas  does 

What  is  the  reason  that  zinc  can  not  decompose  water  alone  ?  How 
may  hydrogen  gas  be  made  by  the  aid  of  zinc  ?  What  are  the  properties 
of  this  gas? 


180  PROPERTIES    OF    HYDROGEN. 

not  exert  any  directly  deleterious  effect ;  and  although  it 
can  not,  of  course,  carry  on  the  functions  of  respiration, 
which  are  acts  of  oxydation,  yet  it  can,  for  a  short  space, 
be  introduced  into  the  lungs  with  impunity.  If  a  person 
whose  lungs  are  inflated  with  it  attempts  to  speak,  his 
voice  resembles  the  feeble  and  shrill  voice  of  a  child. 
This  arises  from  the  small  density  of  hydrogen ;  a  bell 
rung  in  this  gas  emits  almost  as  feeble  a  sound  as  if  rung 
in  a  vacuum. 

One  of  the  most  striking  peculiarities  of  hydrogen  is  its 
great  inflammability  in  contact  with  ox-  Fig.  iei. 

ygen.  If  a  jar,  Fig.  161,  with  a  stop- 
cock at  its  upper  extremity,  be  filled 
with  hydrogen,  and  then,  being  depress- 
ed in  the  water  of  the  trough,  the  cock 
opened  and  a  light  brought  near  the 
hydrogen  as  it  escapes,  it  takes 
fire  at  once,  burning  with  a  pale 
yellow  flame.  Or  if  to  the  mouth 
of  a  bottle  containing  the  mate- 
rials for  generating  hydrogen,  a,  Fig.  162,  a  cork, 
through  which  a  glass  tube,  &,  is  passed,  be  adjust- 
ed, and  after  allowing  the  air  in  the  bottle  to  be  dis- 
placed, a  light  be  applied  to  the  issuing  gas,  it  takes 
fire  and  burns  in  the  same  manner;  an  experiment  com- 
monly described  as  the  philosophical  candle. 

The  following  experiment  proves  three  facts  at  the 
Fig.  163.  same  time:  1.  The  great  lightness  of  hydro- 
gen; 2.  Its  inflammability;  3.  That  it  is  not  a 
supporter  of  combustion.  A  jar,  a,  Fig.  163,  is 
to  be  filled  with  hydrogen  at  the  water-trough, 
and  then/  being  lifted  in  the  air  with  its  mouth 
downward,  a  taper,  placed  on  a  bent  wire,  is  car- 
ried into  its  interior.  As  the  taper  passes  the 
mouth  of  the  jar  there  is  a  feeble  explosion,  and  the  hy- 
drogen taking  fire,  burns  with  a  pale  flame ;  but  as  soon 
as  it  is  immersed  in  the  atmosphere  of  the  gas  the  taper 
is  extinguished.  It  may,  however,  be  relighted  as  it  is 
brought  out  of  the  jar  at  the  burning  hydrogen,  and  this 
may  be  repeated  several  times  in  succession.  The  com- 

What  are  its  relations  to  respiration  ?  How  may  its  combustibility  be 
demonstrated  1  How  may  its  inflammability,  its  non-supporting  power 
and  its  lightness  be  simultaneously  illustrated  ? 


COMBUSTION    OF    HYDROGEN.  1$1 

bustibility  of  the  gas  and  its  quality  of  not  supporting 
combustion  are  obvious  enough,  and  its  lightness  is  proved 
by  the  fact  that  it  does  not  flow  out  of  the  open  mouth  of 
the  jar,  which  it  would  do  at  onee  if  it  were  heavier  than 
atmospheric  air. 

The  application  of  hydrogen  to  aerostatic  purposes  is 
founded  upon  its  small  specific  gravity.  This  property  is 
very  distinctly  illustrated  by  filling  an  India  rubber  gas- 
bag with  hydrogen,  and  having  attached  to  the  stop-cock,  a, 
Fig.  164,  which  closes  it,  a  common  earth-  Fig.  164. 

en-ware  tobacco-pipe,  &,  by  dipping  the 
pipe  in  a  solution  of  soap,  bubbles  may 
be  blown.  These  rise  through  the  air 
with  rapidity  ;  and  if  a  lighted  taper  is 
brought  near  them  as  they  are  ascending, 
the  hydrogen  takes  fire  and  burns  with  a 
yellowish  flame. 

If,  in  a  strong  brass  vessel,  a,  Fig.  165,  we  place  a  mixtui  e 
of  hydrogen  and  atmospheric  air  in  equal  Fig.  165. 
volumes,  and,  having  inserted  the  cork,  c, 
tightly,  pass,  by  the  aid  of  the  ball  and 
wire,  b,  an  electric  spark  through  the  gas, 
Si.  violent  explosion  takes  place,  the  hydrogen  burning  in- 
stantaneously with  the  atmospheric  oxygen,  and  giving 
rise  to  the  production  of  water. 

Musical  sounds  originate  in  vibratory  movements  com- 
municated to  the  air.  If  the  flame  of  a  philosophical  can- 

, for  example,  Ffe 


dle  is  covered  by  a  wide  glass  tube,  as, 
the  neck  of  a  broken  retort,  an  intensely  powerful 
sound  is  emitted.  This  arises  from  the  circum- 
stance that  the  hydrogen  burns  in  the  tube,  giving 
rise  to  a  series  of  small  explosions,  which  follow 
each  other  with  rapidity,  and  these  explosions  throw 
the  air  in  the  tube  into  a  vibratory  state.  Accord- 
ing as  the  tube  is  raised  or  lowered,  these  explo- 
sions occur  with  different  degrees  of  rapidity,  some- 
times producing  a  clattering  sound,  and  then  a  pure  mu- 
sical note. 

Whatever  may  be  the  circumstances  under  which  hy- 


To  what  purpose  is  hydrogen  applied  in  consequence  of  its  lightness  ? 
How  may  this  be  illustrated  on  a  small  scale  ?  When  mixed  with  oxygen 
»r  air,  and  an  electric  spark  passed  through  it,  what  is  the  result  ?  Under 
irhat  circumstances  will  the  flame  of  hydrogen  emit  a  musical  sound  ? 


182  OXYHYDROGEN    BLOW-PIPE. 

drogen  burns,  whether  quietly,  as  in  the  philosophical 
candle,. or  with  trivial  explosions,  as  in  this  tube,  or  with 
a  violent  detonation,  as  in  the  preceding  experiment,  the 
uniform  product  of  the  combustion  is  water.  During  the 
combination  of  these  elementary  bodies  with  each  other  a 
very  great  amount  of  heat  is  given  out,  for  hydrogen 
combines  with  eight  times  its  own  weight  of  oxygen,  a 
greater  proportion  than  is  met  with  in  the  case  of  any 
substance  whatever.  Advantage  is  taken  of  this  in  the 
construction  of  the  oxyhydrogen  blow-pipe,  an  instrument 
invented  by  Dr.  Hare,  which  furnishes  us  with  the  most 
efficient  means  of  obtaining  a  high  temperature.  There 
Fig.  167.  are  several  different  forms  of  this  blow- 
pipe ;  in  some  the  gases  are  mixed  in  the 
proper  proportions  in  a  strong  receiver, 
and  set  on  fire  after  passing  through  a 
Hemming's  safety  tube.  But  it  is  better 
to  keep  them  in  separate  reservoirs,  and 
conduct  them  to  a  common  jet,  where 
they  may  simultaneously  mix  and  be 
burned,  as  is  shown  in  Fig.  167,  where  O  is  the  oxygen 
reservoir,  H  the  hydrogen,  a  b  the  flexible  lead  pipes, 
leading  to  a  common  jet,  c,  at  which  the  gases  are  set  on 
fire.  By  this  instrument  substances  perfectly  infusible 
in  a  common  furnace  melt  at  once.  The  intensity  of  the 
heat  of  this  blow-pipe  depends,  to  a  great  extent,  on  the 
fact  that,  unlike  ordinary  flames,  the  oxyhydrogen  flame 
is,  as  it  were,  solid  j  that  is,  incandescent  throughout  all 
its  parts. 

In  its  general  relations,  hydrogen  possesses  so  many  of 
the  properties  of  the  metallic  class,  that  there  is  every 
reason  to  believe  it  is,  in  reality,  a  metal.  The  facts  of 
its  aerial  form  and  transparency  can  scarcely  be  regard- 
ed as  of  any  weight  against  this  conclusion,  for  the  vapor 
of  mercury  possesses  a  similar  aspect. 

What  is  the  uniform  production  of  its  combustion  1  Why  is  so  much 
heat  evolved  in  the  burning  of  a  mixture  of  oxygen  and  hydrogen  ?  De- 
scribe Hare's  compound  blow -pipe.  What  is  the  peculiarity  of  the  flame  ? 
To  what  class  of  bodies  does  hydrogen  probably  belong  ? 


WATER.  183 


LECTURE  XLI. 

WATER. — Hydrogen  Acids.  —  Water. —  Its  Properties.  — 
Compressibility. — Constitution  of  Water. — Syntheses  of 
Water. — By  Spongy  Platinum. — Determination  of  its 
Composition  by  Weight. — Analysis  of  Water. — Chemi- 
cal Relations  of  W^ater. —  Water  of  Crystallization  and 
Saline  Water. — Acts  as  a  basic,  indifferent,  and  acid 
Body. — Purification. — Deufoxide  of  Hydrogen. 

WATER.     HO  =  9-013. 

HYDROGEN  unites  with  all  the  electro-negative  substan- 
ces, and,  with  many  of  the  more  prominent  ones,  forms 
strong  acids.  The  hydrogen  acids  of  chlorine,  bromine, 
iodine,  and  fluorine  are  all  constituted  upon  the  same 
type,  in  which,  if  the  electro-negative  radical  be  repre- 
sented by  R,  we  have 

HR. 

But  with  oxygen,  instead  of  an  acid,  a  neutral  body  re- 
sults.    This  body  is  common  water. 

Water,  as  will  be  presently  proved,  results  from  the 
union  of  oxygen  and  hydrogen,  one  atom  of  each  of  these 
elements  combining  to  form  one  atom  of  water.     It  is. 
therefore,  a  binary  compound.     Its  symbol  is 
HO. 

By  volume,  it  consists  of  two  of  hydrogen  united  with 
one  of  oxygen;  by  weight,  one  part  of  hydrogen  united 
with  eight  of  oxygen.  These  statements  correspond 
with  the  first,  because  the  hydrogen  atom  is  twice  the 
volume  of  that  of  oxygen  ;  and  the  weight  of  an  atom  of 
oxygen  is  eight  times  that  of  hydrogen. 

Water  is  a  colorless  and  tasteless  body.  It  freezes  at 
32°  F.,  and  boils  at  212°  F.  Its  specific  gravity  is  1-000, 
being  the  standard  of  comparison  of  all  other  liquid  and 
solid  bodies.  The  specific  gravity  of  its  vapor,  steam, 
compared  with  atmospheric  air,  is  0-6201.  It  is  a  com- 
pressible and  elastic  substance.  One  cubic  inch  of  it  at 
62°  weighs  252-45  grains. 

When  hydrogen  unites  with  electro-negative  substances,  what  class  of 
bodies  arise  ?  What  is  the  constitution  of  water  ?  What  are  the  proper- 
ties of  water  ? 


184 


COMPRESSIBILITY    OF   WATER. 


Fig.  168.  The  compressibility  of  water  is  at  once  dem- 
onstrated and  measured  by  an  instrument  in- 
vented by  GErsted,  and  represented  in  Fig.  168. 
It  consists  essentially  of  a  strong  glass  cylinder, 
a  a,  filled  with  water,  upon  which  a  powerful 
pressure  can  be  exerted  by  means  of  a  piston 
driven  by  a  screw,  b.  In  this  cylinder  of  water 
a  gage,  represented  on  a  larger  scale  by  Fig. 
169,  is  placed.  The  gage  consists  of  a  reservoir, 
e,  prolonged  into  a  fine  tube,  f ;  there  is  also  a 
scale  annexed.  The  reservoir  and  part  Fi  169 
of  the  tube  are  filled  with  water,  and  a 
small  column  of  quicksilver,  x,  indicates 
the  point  on  the  tube  to  which  the  water 
The  pressure  exerted  is  measured  by  an 
d. 


reaches, 
air-gagej 

If,  now,  this  instrument  be  placed  in  the  strong 
glass  cylinder,  as  seen  in  Fig.  168,  and  pressure 
exerted  by  turning  the  screw,  the  air  in  the  gage, 
cZ,  contracts  and  indicates  the  amount  of  that  press- 
ure ;  at  the  same  time,  the  small  column  of  mercury, 
x,  descends  in  the  tube,  showing  that  the  water  con- 
tracts, and  measuring  its  amount.  On  turning  the 
_screw  the  other  way,  so  as  to  relieve  the  apparatus 
of  pressure,  the  air-gage  comes  back  to  its  original 
point,  and  the  mercury  in  the  fine  tube  ascends  again. 
It  is  obvious,  therefore,  that  by  this  instrument  we  meas- 
ure the  compressibility  of  the  water  contained  in  the  res- 
ervoir, e,  due  allowance  being  made, for  the  minute  amount 
of  contraction  which  the  glass  of  which  e  is  made,  and 
^.170.  which  is  pressed  equally  on  its  inside  and  outside, 
undergoes;  and  also  for  variations  of  temperature. 
CErsted's  instrument  shows  that  water  is  compress- 
ed 2-s-^J'o  Part  °f  its  volume  for  each  atmosphere 
of  pressure. 

The  constitution  of  water  was  first  clearly  proved 
by  Mr.  Cavendish.  It  can  be  illustrated  in  a  vari- 
ety of  ways.  Thus,  if  over  a  jet  of  burning  hydro- 
gen a  cold  glass  bell  be  suspended,  as  in  Fig.  170, 
it  becomes  soon  covered  with  a  misty  dew,  and, 

Describe  CErsted's  instrument  for  proving  its  compressibility.  What  is 
the  amount  of  its  compressibility  ?  How  may  its  composition  be  synthet- 
ically illustrated  ? 


SYNTHESIS    OP    WATER. 


185 


if  the  experiment  be  prolonged,  drops  of  liquid  finally 
trickle  down  the  sides,  and  may  be  caught  in  a  vessel 
placed  to  receive  them.  When .  examined,  this  liquid  is 
found  to  be  water.  It  has  arisen  from  the  union  of  the 
hydrogen  with  atmospheric  oxygen. 

If  in  a  vessel  over  the  mercurial  trough  twenty  meas- 
ures of  pure  hydrogen  are  added  to  ten  measures  of  pure 
oxygen,  and  a  small  pellet  of  spongy  platinum  passed  up 
through  the  quicksilver,  union  between  the  two  gases 
rapidly  takes  place,  so  that  it  is  usual,  in  order  to  moder- 
ate its  action,  to  mix  the  spongy  platina  previously  with 
a  little  pipe  clay.  As  the  gases  unite,  the  mercury  rises, 
until  at  last  they  have  totally  disappeared.  This  beauti- 
ful experiment  shows  that  the  constitution  of  water  by 
volume  is  2  hydrogen  to  1  oxygen,  as  has  already  been 
said. 

The  composition  of  water  by  weight  was  determined 
by  Berzelius  as  follows :  Let  a  flask,  a,  Fig.  171,  con- 
Fig-.  171. 


taining  zinc  and  dilute  sulphuric  acid,  be  connected  by  a 
bent  tube,  Z>,  with  another  tube,  d,  containing  chloride  of 
calcium ;  the  hydrogen  which  is  consequently  evolved 
from  the  flask  deposits  any  small  quantity  of  water  it  may 
be  contaminated  with  in  the  bulbs  c  c,  and  then  passing 
through  the  chloride  of  calcium  tube,  J,  is  made  perfectly 
dry.  The  tube  d  is  connected  with  a  tube  of  hard  glass, 
on  which  a  bulb,  e,  is  blown.  This  bulb  is  filled  with  a 
known  weight  of  oxide  of  copper,  which  can  be  raised  tt 
a  red  heat  by  means  of  a  spirit  lamp,  h  ;  and  as  the  dry 
hydrogen  passes  over  the  ignited  oxide  it  reduces  it,  form- 
How  may  the  constitution  of  water  be  proved  synthetically  by  spongy 
platinum  ?  Describe  the  method  of  Berzelius  for  determining  the  compo- 
sition of  water  by  weight. 

Q2 


186 


ANALYSIS    OF    WATER. 


ing  with  its  oxygen  water,  and  leaving  pure  metallic  cop- 
per. The  water  thus  produced  is  partially  collected  in 
the  bulby)  and  the  rest  of  it  is  detained  by  a  second  chlo- 
ride of  calcium  tube,  g. 

If,  therefore,  we  weigh  the  tube  e  before  and  after  the 
experiment,  in  the  latter  instance  its  weight  will  be  less 
than  the  former,  the  difference  being  due  to  the  amount 
of  oxygen  which  has  been  removed.  If,  also,  we  weigh 
the  tubes  f  and  g  before  and  after  the  experiment,  in  the 
latter  case  they  weigh  more  than  in  the  former,  the  differ- 
ence being  the  weight  of  the  water  produced.  Thus,  it 
will  be  found  that  for  every  eight  grains  that  the  oxide 
of  copper  has  lost  nine  grains  of  water  have  been  pro- 
duced, showing  that  the  constitution  of  water  is  by  weight 
8  of  oxygen  to  1  of  hydrogen. 

Fig.  172.  The  composition  of  water  may  also  be 

proved  analytically  as  well  as  synthetically. 
It  has  been  already  stated  that  this  can  be 
done  by  the1  Voltaic  battery  in  a  very  sat- 
isfactory manner.  An  apparatus  suited  for 
this  purpose  is  shown  in  Fig.  172.  The 
polar  wires  of  the  battery  enter  the  sides 
of  a  globular  glass  vessel  full  of  water,  and 
over  their  terminations  tubes  are  inverted 
in  which  to  receive  the  gases.  The  hy- 
drogen is  double  the  volume  of  the  ox- 

ygen- 

Another  form  of  the  same  apparatus 
is  seen  in  Fig.  173.  In  a  bent  tube 
full  of  water,  the  platina  wires,  N  P, 
are  introduced  by  means  of  corks.  On 
the  current  passing,  oxygen  is  collected 
in  one  of  the  branches  of  the  tube  and 
hydrogen  in  the  other. 

Lavoisier  determined  the  composition 
of  water  by  passing  its  vapor  over  pieces 
of  iron  made  red  hot  in  a  tube.  Thus, 
if  from  the  retort,  a,  Fig.  174,  containing  boiling  water, 
steam  is-  passed  through  a  red-hot  iron  tube,  c  c,  filled 
with  turnings  of  iron,  or  iron  wire,  decomposition  takes 
place,  black  oxide  of  iron  forming,  and  hydrogen  gas 
escaping  by  the  tube,jf,  into  the  gas-holder,  m  n. 

How  may  the  analysis  of  water  be  effected  ?    Describe  the  principle  of 
Lavoisier's  analysis  of  water. 


DECOMPOSITION   OF   WATER. 


187 


The  chemical  relations  of  water  are  of  the  utmost  im- 
portance. It  exerts  a  more  general  solvent  action  than 
any  other  liquid  known,  holding  in  solution  gaseous  and 
solid  substances,  acids,  alkalies,  and  salts.  As  respects 
gaseous  bodies,  the  quantity  which  water  will  take  up  is 
to  a  considerable  extent  dependent  on  pressure,  and  in 
the  case  of  salts,  an  increase  of  temperature  very  fre- 
quently increases  its  solvent  powers.  Salt-crystals  some- 
times contain  a  very  considerable  quantity  of  it,  as  is  shown 
in  the  case  of  common  alum,  of  which,  if  a  Fig.  175. 
mass  be  put  upon  a  red-hot  brick,  Fig.  175, 
it  melts  in  its  own  water  of  crystallization,  and, 
after  a  great  quantity  of  steam  is  thrown  off, 
a  dry  residue  remains.  Crystals  often  con- 
tain water  in  two  different  states,  one  portion 
known  under  the  name  of  water  of  crystallization,  which 
may  generally  be  expelled  by  a  moderate  heat ;  another 
portion  known  as  saline  water,  which  is  with  much  more 
difficulty  driven  off.  In  the  works  on  chemistry,  the  for- 
mulae are  constructed  so  as  to  indicate  these  different  con- 
ditions of  the  water  :  Aq  (aqua.)  being  the  symbol  for  the 
water  of  crystallization,  and  HO  for  the  saline  water;  thus, 
FeO  +  SOS  +  HO  +  6Aq, 

How  does  water  compare  with  other  bodies  as  respects  solvent  power? 
What  is  meant  by  water  of  crystallization,  and  saline  water?  How  is 
this  difference  indicated  in  formulae  ? 


188  DEUTOXIDE  OF  HYDROGEN. 

is  the  symbol  for  green  vitriol,  which  is  therefore  a  sul- 
phate of  the  protoxide  of  iron,  with  one  atom  of  saline 
water  and  six  of  water  of  crystallization.  The  latter  is 
easily  driven  off  by  heat,  but  the  former  only  at  high  tem- 
peratures, or  by  l>eing  replaced  by  some  other  body. 

Water  unites  with  many  acids  with  great  energy.  If 
mixed  with  sulphuric  acid,  and  a  thermometer  immersed, 
the  temperature  will  run  up  rapidly  to  above  212°.  With 
basic  bodies,  the  same  results  may  be  obtained  as  when 
quicklime  is  sprinkled  with  water,  or  potash  and  soda 
dissolved  in  it :  toward  acids  water  acts  as  a  base ;  toward 
bases  it  acts  as  an  acid  ;  and  toward  salts  as  an  indifferent 
body. 

As  found  in  nature,  water  is  always  impure.  Rain- 
water and  melted  snow  contain  the  various  soluble  gases 
which  are  in  the  air;  spring,  river,  well,  and  mineral 
waters  the  soluble  bodies  of  the  strata  through  which  they 
have  flowed ;  from  these  it  can  only  b<5  purified  by  the 
process  of  distillation. 

DEUTOXIDE  OF  HYDROGEN.  HO2  =  17-013. 
There  is  another  compound  of  hydrogen  and  oxygen, 
the  deutoxide  of  hydrogen.  It  contains  twice  the  amount  of 
oxygen  found  in  water,  and  is  characterized  by  a  remark- 
able facility  of  decomposition.  It  is  a  liquid  substance, 
possesses  bleaching  powers,  and  is  heavier  than  water 


LECTURE  XLII. 

NITROGEN. — Preparation  of  Nitrogen. — Properties. — Its 
Indifferent  Nature. — Its  Oxygen  Compounds. — Atmos- 
pheric Air. —  Constitution  of. — Dimensions  of. — Rela- 
tions to  Organization. — Density  and  Temperature. — Fix- 
ed and  Variable  Constituents. — Experimental  Proofs  of 
its  Pressure. 

NITROGEN.     N=  14-19. 

NITROGEN  gas  is  most  readily  procured  from  the  atmos- 
pheric air  by  burning  phosphorus  in  a  bell  jar  over  the 

"What  is  the  relation  of  water  to  acids,  bases,  and  salts  ?  By  what  pro- 
cess is  water  purified  ?  "What  is  the  constitution  and  properties  of  the 
deutoxide  of  hydrogen  ?  What  is  the  process  for  preparing  nitrogen  by 
phosphorus  ? 


NITROGEN    GAS.  189 

pneumatic  trough.     If  a  piece  Fig.  176. 

of  phosphorus  be  laid  in  a  cup 
(Fig.  176)  and  set  on  fire,  all 
the  oxygen  in  the  air  of  the  jar, 
a,  will  be  consumed,  white  flakes 
of  phosphoric  acid  forming,  and 
these,  being  finally  dissolved  in 
the  water  of  the  trough,  d,  there 
is  left  behind  nitrogen,  contami- 
nated to  a  small  extent  by  the 
vapor  of  phosphorus. 

If  nitrate  of  ammonia  be  placed  in  a  retort,  and  the  tem- 
perature raised  until  it  emits  protoxide  of  nitrogen,  and 
at  that  moment,  by  means  of  a  wire  passing  through  a 
cork  in  the  tubulure,  a  piece  of  zinc  is  lowered  down  upon 
the  melted  mass,  oxide  of  zinc  is  produced,  and  nitrogen 
gas  escapes.  The  decomposition  is  very  simple, 
NO  . .  Zn  =  Zn  O  . .  N. 

Nitrogen  gas  is  a  colorless,  tasteless,  and  inodorous 
body,  very  sparingly  soluble  in  water,  that  liquid  dissolv- 
ing but  1^  per  cent,  of  its  volume.  It  is  lighter  than  at- 
mospheric air,  its  specific  gravity  being  0-976.  Its  atomic 
weight  is  14'19.  It  does  not  support  combustion  nor  respi- 
ration, and  from  the  latter  circumstance  obtained  formerly 
the  name  of  azote  ;  but  it  does  not  exert  any  directly  pois- 
onous agency  on  the  animal  system. 

Nitrogen  gas  is  little  disposed  to  unite  with  other  bod- 
ies, except  when  either  it  or  they  are  in  the  nascent  state. 
Its  compounds,  too,  are  prone  to  decompose  from  trivial 
causes ;  hence  it  is  among  them  that  we  find  some  of  the 
most  remarkably  detonating  bodies.  Many  animal  and 
vegetable  substances,  into  the  composition  of  which  it 
enters,  are  characterized  by  the  facility  with  which  they 
tend  to  undergo  putrefactive  changes,  and,  as  we  shall  here- 
after find,  ferments  owe  their  remarkable  powers  to  the 
presence  of  this  element. 

Nitrogen  unites  with  oxygen,  and  forms  five  different 
bodies, 

NO . . .  NOZ . . .  NO3 . . .  NO, . . .  NO5. 

How  may  it  be  made  from  nitrate  of  ammonia  ?  What  are  the  proper- 
ties of  this  gas  ?  Why  does  it  give  rise  to  so  many  explosive  bodies  ? 
To  what  is  the  property  of  ferments  due  ?  How  many  compounds  of  oxygen 
and  nitrogen  are  there  ? 


190 


THE    ATMOSPHERIC    AIR. 


Their  names  are 

Protoxide  of  nitrogen.  Nitrous  acid. 

Deutoxide  of  nitrogen.  Nitric  acid. 

Hypohitrous  acid. 

With  oxygen,  also,  it  forms  atmospheric  air;  "but  this  is  a 
mixture,  and  not  a  compound. 

ATMOSPHERIC  AIR. 

The  mechanical  properties  and  constitution  of  the  at- 
mosphere are  so  important,  that  I  shall  here  introduce  the 
consideration  of  them  before  passing  to  the  description  of 
the  oxides  of  nitrogen. 

The  atmosphere  consists  chiefly  of  oxygen  and  nitrogen 
gases,  in  the  proportion  of  about  21  volumes  of  the  former 
to  79  of  the  latter.  It  also  contains  a  minute  but  essential 
quantity  of  carbonic  acid,  which,  however,  varies  at  dif- 
ferent times,  10,000  parts  of  air  containing,  on  an  average, 
about  five  parts  of  this  gas.  Besides  these,  there  are  found 
in  it  variable  quantities  of  the  vapor  of  water,  and  traces 
of  ammonia,  sulphureted  hydrogen,  and  carbureted  hy- 
drogen. It  is  a  colorless,  invisible,  elastic  substance,  815 
times  lighter  than  water,  and  is  taken  as  the  standard  of 
comparison  for  the  specific  gravity  of  gases.  Its  specific 
gravity  is,  therefore,  =  TOGO.  One  hundred  cubic  inch- 
es of  it  weigh,  at  the  mean  temperature,  and  pressure  very 
nearly  31  grains. 

There  are  many  methods  by  which  the  analysis  of  the 
air  can  be  effected.  lire's  eudiom- 
eter, Fig.  177,  which  consists  of  a 
siphon  tube,  closed  at  one  end  and 
open  at  the  other,  may  be  used  for 
this  purpose.  Into  the  closed  branch 
of  the  instrument,  which  is  also  grad- 
uated, a  measured  quantity  of  air  is 
introduced,  and  to  it  is  added  an 
equal  volume  of  hydrogen.  The 
bend  of  the  tube  is  occupied  by  wa- 
ter, as  shown  in  the  figure,  a  column 
of  air  intervening  between  this  water  and  the  open  ex 
tremity  of  the  tube.  On  this  the  thumb  is  closely  pressed, 

Of  what  is  the  atmospheric  air  composed?  "What  is  its  specific  grav. 
ity  1  What  is  the  weight  of  100  cubic  inches  of  it  1  How  may  it  be  an. 
alyzed  by  Ure's  eudiometer? 


Fig.  r 


ANALYSIS    OF    THE    AIR.  191 

as  represented,  and  an  electric  spark  passed  through  the 
instrument  by  the  aid  of  its  platina  wires.  This  sets  the 
gases  on  fire  ;  the  column  of  air  beneath  the  thumb  acting 
like  a  spring  to  repress  the  movement  at  the  time  of  the 
explosion.  The  amount  of  gas  then  left  is  ascertained  on 
the  divisions,  and  one  third  of  the  deficit  represents  the 
quantity  of  oxygen  originally  present. 

To  enable  the  experimenter  to  operate  on  larger  quan- 
tities of  gas,  Brunner's  instrument  may  Fif  17g 
be  used.  It  consists  of  a  tube,  a  be,  with 
three  bulbs  blown  upon  it ;  these  bulbs 
are  filled  with  cotton  which  has  been  im- 
pregnated with  melted  phosphorus.  The 
tube  is  attached,  by  means  of  a  cork,  to 
a  glass  vessel,  d,  filled  with  mercury.  On 
opening  the  stop-cock,  e,  the  mercury 
flows  out,  atmospheric  air  introducing 
itself  by  a  b  c,  and  its  oxygen  being  re- 
moved by  means  of  the  extensive  surface 
of  phosphorus  which  the  cotton  presents. 
Consequently,  by  measuring  the  mercury 
which  has  flowed  out  we  ascertain  the 
quantity  of  nitrogen  introduced  into  the  vessel  d,  and  the 
increased  weight  of  the  tube  a  b  c  determines  the  amount 
of  oxygen. 

The  result  of  such  experiments  shows  that  the  atmos- 
pheric air  is  composed  of  from  20-79  to  21-08  parts  of 
oxygen  in  100  volumes.  By  weight,  its  constitution  is 
about, 

Oxygen    .    . 
Nitrogen  .    . 

The  earth's  atmosphere  does  not  extend  indefinitely 
into  space,  but  terminates  at  an  altitude  of  about  fifty 
miles.  It  forms,  therefore,  a  mere  film  on  the  face  of 
the  earth,  for  the  diameter  of  the  globe  is  nearly  8000 
miles.  If  a  representation  of  it  were  placed  on  a  common 
twelve-inch  globe,  it  would  scarcely  be  one  eighth  of  an 
inch  thick. 

Its  relations  to  the  world  of  organization  are  full  of  in- 
terest. All  plants  come  from  it  and  all  animals  return  to 

How  by  Brunner's  instrument  ?  What  is  its  constitution  by  volume  and 
by  weight  ?  To  what  distance  does  it  extend  ? 


192 


DENSITY    OF    THE    AIR. 


it,  so  that  it  stands  as  the  bond  of  connection  between 
these  orders  of  life. 

As  we  ascend  to  more  elevated  regions  the  air  becomes 
less  dense,  for  the  obvious  reason  that,  as  it  is  a  very  com- 
pressible body,  those  portions  of  it  nearest  the  ground 
have  to  sustain  the  weight  of  the  superincumbent  mass, 
and  are  therefore  more  dense ;  but  in  the  higher  regions, 
where  the  superincumbent  pressure  is  less,  the  air  is  more 
rare,  as  is  shown  in  the  following  table : 


Height  in  Miles. 

Volume  of  Air. 

Barometric  Inches. 

o- 

1 

30- 

2-705 

2 

15' 

5-41 

4 

7.5 

8-115 

8 

3-75 

10-82 

16 

1-875 

13-525 

32 

•9375 

16-23 

64 

•46875 

which  also  shows  that  the  great  mass  of  the  atmosphere  is 
comprehended  within  a  very  short  distance  of  the  earth's 
surface.  At  different  altitudes  it  is  of  very  different  tem- 
peratures, being  colder  as  the  altitude  is  greater. 

Of  the  constituents  of  the  air,  the  oxygen  and  nitrogen 
are  usually  spoken  of  as  fixed,  the  carbonic  acid,  ammo- 
nia, and  water  as  variable.  There  are  causes  in  operation 
which  tend  continually  to  impress  changes  in  the  amount 
of  all  these  bodies.  Every  process  of  combustion,  and  the 
respiration  of  every  animal,  remove  oxygen  and  replace 
it  by  carbonic  acid.  But  the  growth  of  plants  has  the  re- 
verse action,  removing  carbonic  acid  and  replacing  it  by 
oxygen,  so  that  for  many  centuries  in  succession  the  con- 
stitution of  the  atmosphere  is  unchanged. 

Of  the  mechanical  properties  of  the  air,   the   first  to 
179  which  we  have  to  direct  our  attention  is  its  press- 
ure, which  takes  effect  equally  in  all  directions,  up- 
ward, downward,  and  laterally.     Thus,  if  we  take 
\a   a  glass  tu^e  several  feet  long,  a,  Fig.  179,  closed 
at  one  end  uud  open  at  the  other,  and  having  filled 
it  full  of  water,  place  over  the  mouth  of  it  a  piece 
of  card,  b,  and  turn  it  upside  down,  the  card  will 
not  fall  off,  nor  the  water  flow  out ;  they  remain, 
as  it  were,  suspended  on  nothing,  but  in  reality  sus- 

What  are  its  relations  to  animals  and  plants  ?  Why  does  its  density 
decrease  with  the  altitude  ?  How  does  its  temperature  vary  ?  Which 
are  the  fixed,  and  which  the  variable  constituents  of  the  air  ?  Give  sonwe 
illustrations  of  the  upward  pressure  of  the  air.  '.  *  •& 


PRESSURE    OF    THE    AIR. 


193 


tained  by  the  upward  pressure  of  the  air.  Or  if  we  take 
a  bottle,  a,  Fig.  ISO,  with  a  hole,  b,  half  an  inch 
in  diameter  in  the  bottom  of  it,  and  having  filled 
it  with  water,  close  the  mouth  of  it  with  the  fin- 
ger, it  may  be  held  up  in  the  air  without  the  wa- 
ter flowing  out,  although  the  aperture  b  is  wide 
open.  In  this  instance,  again,  it  is  the  upward 
pressure  of  the  air  which  sustains  the  liquid. 

Let  the  glass  globe  a,  Fig.  181,  with  its  neck 
5,  be  inverted  in  some  water  contained  in  ajar, 
c,  and  the  whole  covered  by  an  air-pump  re- 
ceiver. As  the  receiver  is  exhausted,  bubbles 
of  air  pass  through  the  water  and  escape  away, 
but  as  soon  as  the  pressure  is  restored  the 
water  is  forced  out  of  the  jar  upward  into  the 
globe. 

The  air-pump  enables  us  to  exhibit  in  a  very  striking 
manner  many  of  the  chief  mechanical  properties  of  the  at- 
mosphere. Thus,  if  upon  the  plate  of  it  there  Fi 
be  placed  a  glass  receiver,  a,  Fig.  182,  as  soon 
as  the  air  is  exhausted  from  its  interior,  the  su- 
perincumbent pressure  retains  the  glass  so  firm- 
ly in  contact  that  it  is  impossible  to  lift  it  off, 
Fig.  184.  but  as  soon  as  the  air  is  readmit- 
ted it  can  be  easily  removed.  If 
within  the  receiver  a  a  smaller  one,  b,  be 
placed,  and  exhaustion  made,  while  a  is  fixed 
b  can  be  easily  moved  by  shaking  the  pump, 
but  on  letting  in  the  air,  a  becomes  loose  and 
b  firmly  pressed  in  contact  with  the  plate. 

If  over  the  mouth  of  a  Fig.  183. 

jar,  Fig.  183, placed  upon 
the  pump,  the  palm  of 
cu  the  hand  be  laid,  as  the 
air  is  exhausted  it  is 
pressed  in  close  contact 
with  the  jar,  and  can  only 
be  removed  by  the  exertion  of  a  very  con- 
siderable force. 

On  a  small  plate,  a,  Fig.  184,  furnish- 
ed with  a  stop-cock,  b,  terminating  in  a  fine 

Give  an  illustration  of  its  downward  pressure.     Describe  the  experi- 
ment represented  in  Fi?.  183. 


194  PRESSURE    OF    THE    AIR. 

jet,  c,  let  there  be  placed  a  tall  glass  receiver.  The  stop- 
cock being  now  screwed  into  the  pump  and  opened,  the 
air  may  be  exhausted  from  the  interior  of  the  receiver 
and  the  stop-cock  closed.  But  being  now  opened  under 
the  surface  of  some  water  in  a  cup,  the  water  passes 
through  the  jet  and  rises  to  the  top  of  the  jar,  forming  a 
fountain  in  vacuo. 


LECTURE  XLIII. 

ATMOSPHERIC  AIR. — Pressure  of  the  Air. — Simple  Means 
of  Exhaustion. — Determination  of  the  Weight  of  Air. — 
Amount  of  Pressure. — Elasticity  of  Air. — Exists  in  the 
Pores  of  Bodies. — Respiration  of  Fishes. — Measure  of 
Elastic  Force. 

THE  Magdeburg  hemispheres,  invented  by  Otto 
Guerick,  who  also  invented  the  air  pump,  illustrate  in  a 
very  striking  manner  atmospheric  pressure.  They  con- 
Fig.  185.  sist  of  a  pair  of  brass  hemispheres,  a  b,  Fig. 
185,  with  handles  ;  they  fit,  without  leakage,  to 
each  other  by  a  flange,  so  as  to  form  a  perfect 
sphere.  One  of  them  has  a  stop-cock,  through 
which  the  air  may  be  exhausted,  and  on  this 
being  done,  it  will  be  found  almost  impossible 
to  pull  them  apart,  though  as  soon  as  the  air  is 
readmitted,  and  its  pressure  restored  to  the  in- 
terior, they  will  fall  asunder  by  their  own  weight. 

If  over  the  mouth  of  an  open  receiver,  a,  Fig.  186,  a 
Fig.  186.  piece  of  bladder  be  tightly  tied  with  a  waxed 
thread,  when  the  air  is  exhausted  the  bladder 
becomes  deeply  depressed  into  a  spherical  con- 
cavity by  the  superincumbent  pressure,  and 
finally  bursts  inward  with  a  loud  explosion. 

It  is  upon  the  principle  of  atmospheric  press- 
ure that  the  various  instruments  used  by  surgeons  for  cup- 
ping act.  One  of  the  most  simple  methods  of  performing 
this  operation  is  to  place  the  cupping  glass  for  a  moment 
over  the  flame  of  a  spirit  lamp,  and  then  transfer  it  rapid- 
Describe  the  fountain  in  vacuo.  What  are  the  Magdehurg  hemispheres  ? 
What  is  the  principle  illustrated  in  these  various  experiments  ?  How 
is  the  process  of  cupping  performed  ? 


WEIGHT    OF    AIR. 


195 


ly  to  the  skin.  Spirits  of  wine,  when  burning,  forms  a 
very  large  quantity  of  steam,  which,  of  course,  fills  the  in- 
terior of  the  glass  in  a  rarefied  state  by  reason  of  the  hicrh 
temperature  of  the  flame.  As  soon  as  this  steam  con- 
denses a  vacuum  is  formed,  and  the  soft  surface  on  which 
the  cup  is  placed  is  pressed  into  its  interior. 

For  mahy  of  these  experiments,  an  air  pump  is  not  nec- 
essarily required,  but  simple  contrivances  will  answer  in 
its  stead.  Thus,  if  we  take  an  eight-ounce 
rial,  a,  Fig.  187,  and  fit  to  the  mouth  of  it 
a  cork,  b,  through  which  there  passes  a  piece 
of  glass  tube,  c,  drawn  into  a  narrow  jet  at 
one  extremity,  but  open  at  the  other,  by  pla- 
cing  the  finger  over  the  opening  and  intro- 
ducing it  into  the  mouth,  the  air,  by  the  ac- 
tion of  the  tongue  and  the  muscles  of  the  mouth,  may  be 
sucked  out  to  a  great  extent ;  and  when  the  exhaustion 
has  been  carried,  by  this  means,  as  far  as  possible,  by 
pressing  the  finger  over  the  opening,  it  will  close  ft,  act- 
ing, therefore,  as  a  valve.  And  now,  if  the  bottle  be  turned 
upside  down,  as  at  e,  the  tube  dipping  beneath  some  wa- 
ter in  a  cup,  as  soon  as  the  fin- 
ger is  removed  the  water  is  press- 
ed upward,  and  forms  a  fountain 
in  vacuo. 

The  pressure  of  the  air  depends 
primarily  on  the  fact  that  it  is  a 
heavy  body,  as  may  be  proved  by 
the  direct  experiment  of  weighing 
it.  For  this  purpose,  let  a  light 
glass  flask,  a,  Fig.  188,  fitted  with 
a  stop-cock,  be  counterpoised  at 
the  balance ;  then  let  the  air  be 
exhausted  from  it,  and  its  weight 
determined  again.  It  will  now 
be  found  lighter  than  before ;  but 
upon  opening  the  stop-cock  it 
will  regain  its  original  weight. 
Experiments  made  in  this  man- 
ner show  that  a  flask  contain- 
ing 100  cubic  inches  will,  when 

Describe  a  simple  method  by  which  partial  exhaustion  may  be  pro- 
duced by  the  mouth.    How  may  the  weight  of  air  be  directly  ascertained  1 


Fig.  188. 


196 


SPECIFIC    GBAVITY    OF    GASE3. 


Fig.  189. 


exhausted,  weigh  about  thirty-one  grains  less,  and  there- 
fore we  infer  that  that  is  the  weight  of  100  cubic  inches 
of  atmospheric  air. 

Atmospheric  air  is  used  as  the  standard  of  comparison  of 
the  specific  gravities  of  other  gaseous  bodies.  The  process 
for  the  determination  is  very  simple.  A  glass  globe,  g, 

Fig.  189,  holding  20  or  30  cu- 
bic inches,  is  exhausted  of  air, 
and  by  means  of  the  stop- 
cocks, e  d,  attached  to  the  jar, 
c,  containing  the  gas  to  be 
tried.  This  gas,  which  is  con- 
fined by  mercury,  has  been 
passed  through  the  drying 
tube,  «,  by  the  delivering 
tube,  b,  into  the  jar,  which 
should  be  graduated.  On 
opening  the  cocks,  e  d,  the 
gas  flows  into  the  exhausted 
globe  ;  the  quantity  introduced  may  be  determined  on  the 
graduation,  and  its  weight  ascertained  by  the  balance. 

There  are  several  different  methods  of  stating  the 
amount  of  the  mean  pressure  of  the  air ;  thus,  we  say  that 
it  is  equal  to  15  pounds  on  the  square  inch,  or  to  a  col- 
umn of  mercury  30  inches  long,  or  to  a  column  of  water 
30  feet  long. 

That  air  is  a  highly  elastic  substance,  can  be  readily 
^    J90    shown.     Under  a  receiver  (Fig.  190)  let  there 
be  placed   a  half-blown  bladder,  the  neck  of 
which  is  tightly  tied  ;  as  the  air  is  removed  from 
the  receiver  the  bladder  distends,         Fig.  IQI. 
but,  on  restoring  the  pressure,  it 
becomes  as  flaccid  as  it  was  be- 
fore, showing  that  the  air  included 
in  it  expands  and  contracts  as  the 
pressure  upon  it  is  made  to  vary. 

This  may  be  still  better  shown  by  taking 
a  small  India-rubber  bag  (Fig.  191),  the 
mouth  of  which  is  closed  tightly,  and  using 


In  what  manner  may  the  relative  weight  of  other  gases  be  determined  ? 
What  is  the  pressure  of  the  air  on  a  square  inch  equal  to  ?  What  is  nearly 
the  equivalent  length  of  a  mercurial  and  water  column*?  How  may  the 
elasticity  of  air  be  illustrated  ? 


ELASTICITY    OF    AIR. 


197 


Fig.  192. 


it  instead  of  the  bladder  in  the  last  experiment.  On  rare- 
fying the  air  in  the  receiver,  the  bag  begins  to  dilate,  and 
may  be  extended  to  several  times  its  original  dimensions, 
as  shown  in  the  dotted  line ;  but  as  soon  as  the  pressure 
is  restored,  it  returns  to  its  original  size. 

Nor  does  this  expansion  take  place  with  an 
inconsiderable  force.  If  a  flaccid  bladder  be 
placed,  as  in  Fig.  192,  with  several  heavy  lead- 
en weights  put  upon  it,  as  soon  as  it  is  caus- 
ed to  dilate  by  removing  the  pressure,  it  will 
push  up  the  weights.  Nor  does  it-lose  its 
elastic  force  or  spring  by  being  long  pent 
up  in  close  vessels.  Some  of  the  old  chem- 
ists kept  air  compressed  in  copper  globes  for 
months,  and  found  that,  as  soon  as  an  opening  was  made 
for  it,  it  expanded  to  its  original  dimensions. 

Let  there  be  taken  a  glass  bulb,  a  (Fig.  193),  the  open 
neck  of  which,  £,  dips  beneath  some  water  in      Fig.  193. 
a  jar,  e,  and  let  the  bulb  and  tube  be  full  of 
water,  with  the  exception  of  a  small  space  oc- 
cupied by  atmospheric  air.     On  covering  the 
apparatus  with  an  air-pump  receiver,  d,  and 
exhausting,  the  bubble  of  air,  a,  gradually  ex- 
pands, and  after  a  time,  as  the  action  of  the 
machine  is  continued,  fills  the  entire  glass,  both 
bulb  and  tube  ;   but  as  the  pressure  is  restored,  it  con- 
tracts again,  and  goes  back  to  its  original  size. 

By  taking  advantage  of  the  expansibility  of  air  under 
Fig.  194.  reduction  of  pressure,  we  are  able  to  dem-  pigi  195< 
onstrate  its  existence  in  the  pores  of  many 
bodies ;  thus,  if  we  place  in  glasses  of 
water  an  egg  (Fig.  194),  an  apple  (Fig. 
195),  or  other  such  pb^ects,  and,  covering 
them  with  a  receiver,  exhaust,  we  shall 
see  innumerable  bubbles  of  air  escaping 
through  the  water.  The  same  observa- 
tion may  be  made  in  the  case  of  many 
liquids  which  hold  gaseous  substances  dis- 
solved. A  glass  of  ale  placed  in  an  exhausted  receiver 

How  may  the  elasticity  of  air  be  shown  by  an  India-rubber  bag  ?  Give 
an  illustration  of  the  amount  of  this  force.  How  may  the  presence  of  air 
be  detected  in  the  pores  of  solid  bodies  ?  How  may  air  be  shown  to  exist 


dissolved  in  liquids 


R2 


193 


RESPIRATION    OF    FISHES. 


Fig.  198. 


Fig.  196.      (Fig.  196)  foams  from  the  escape  of  carbonic 
acid  gas,  and  even  clear  spring  or  river  water, 
examined  in  the  same  manner  (Fig.      Fig.  197. 
197),  is  found  to  contain   a  large 
quantity  of  air  in  solution. 

This  last  fact  is  of  considerable 
importance,  for  it  is  by  the  aid  of 
this  air  that  the  respiratory  function 
of  fishes  is  carried  forward.  On 
examination,  however,  it  is  found  that  this  is 
not  true  atmospheric  air, 
but  a  mixture,  which  is  richer  in  oxy- 
gen. The  atmosphere  contains  21  per 
cent,  of  oxygen,  but  this  gas  contains 
33.  The  cause  of  the  difference  is  the 
unequal  solubility  of  oxygen  and  nitro- 
gen ;  for  the  former  gas,  being  much 
the  more  soluble,  the  water  takes  up 
relatively  a  greater  portion  of  it  from 
the  air.  Fishes,  therefore,  respire  this 
gas,  its  richness  in  oxygen  making 
up. for  its  inferior  amount;  and  when 
they  are  placed  in,  water  which  has 
been  in  an  exhausted  receiver,  they  die.  Their  move- 
ments, also,  are,  to  a  certain  extent,  regulated  by  the  air 
contained  in  a  receptacle,  or  bladder,  in  their  bodies ;  by 
the  compression  of  it  they  can  descend,  and  by  its  expan- 
sion rise.  If  they  be  placed  in  water  in  a  partially  ex- 
hausted receiver,  they  float  on  the,  surface,  or  can  only 
descend  to  the  bottom  for  a  moment  by  violent  muscular 
exertion. 

The  necessity  of  air  to  the  support  of  com- 
bustion may  be  illustrated  by  comparing  the 
length  of  time  a  candle  will  burn  in  a  large 
receiver  full  of  air,  and  in  the  same  exhaust- 
ed, Fig.  199.  In  the  latter  case  it  speedily 
dies  out,  the  smoke  descending  to  the  bottom 
of  the  jar  in  the  rarefied  medium  around. 

Substances  prone  to  decay,  such  as  meats 
and  fruits,  may  be  preserved  for  a  length  of 
time  in  vessels  void  of  air.  The  process  is 

Of  what  use  is  the  air  dissolved  in  water  ?    What  is  its  composition  7 
How  may  the  necessity  of  air  to  the  support  of  combustion  be  proved'? 


Fig.  199. 


PRESERVATION    OF    FRUITS. 


199 


illustrated    in  Fig.  200.     The  F^.aoo. 

fruits  are  placed  in  a  large  jar 
closed  by  a  sound  cork,  covered 
with  sealing-wax.  A  small  hole 
is  made  through  the  cork,  and 
the  jar  covered  by  an  air-pump 
receiver.  On  exhausting,  the 
air  passes  out  through  the  hole, 
and  when  the  vacuum  is  per- 
fect the  hole  is  closed  by  melt- 
ing the  wax  by  the  sunbeams 
converged  by  a  convex  lens, 
the  access  of  the  air  being  thus 
cut  off. 

From  the  foregoing  experiments  and  considerations,  it 
appears  that  the  primary  fact  in  pneumatics  is,  that  the 
air  has  weight ;  from  this,  by  a  necessary  consequence, 
arises  its  pressure  and  the  inequality  of  density  of  the  at- 
mosphere at  different  altitudes.  It  also  follows  that  the 
elastic  force  of  the  air  must  be  precisely  equal  to  the 
pressure  upon  it.  In  any  given  stratum  of  air,  as,  for  in- 
stance, that  which  rests  upon  the  surface  of  the  earth,  the 
pressure  of  the  superincumbent  mass  is  equipoised  by  the 
elastic  force  ;  if  the  elastic  force  were  less,  compression 
would  ensue  ;  if  greater,  dilatation.  The  pressure  and  the 
elastic  force  must,  therefore,  be  equal  to  each  other. 


LECTURE  XLIV. 

ATMOSPHERIC  AIR. —  The  Barometer. — Description  of  it. — 
Cause  of  the  Phenomenon. — Proof  that  it  is  the  Pressure 
of  the  Air. — History  of  the  Invention. — PaschaVs  Ex- 
periment.— Illustrations  of  the  Nature  of  Pressure. — 
Variability  of  Pressure. — Point  of  Perpetual  Congela- 
tion.— Local  Disturbances  in  the  Constitution  of  the  Air. 
— Diffusion  of  Gases. —  The  Air  is  a  Mixture. — Mar- 
riotte's  Law. — Gay-Lussac's  and  Rudberg's  Law. 

IF  we  take  a  tube  of  glass,  a  b,  Fig.  201,  page  200,  more 

By  what  means  may  objects  be  preserved  from  its  influence  ?    What 
is  the  relation  between  the  pressure  and  the  elastic  force  of  the  air  ? 


200  Tfi£    BAROMUTER. 

Fig.  201.  ^an  thirty  inches  long,  closed  at  one  end  and  open 
at  the  other  end,  and,  having  filled  it  with  quick- 
&  silver,  invert  it  in  a  cup,  c, filled  with  that  metal,  the 
mercury  will  not  flow  out  of  the  tube,  but  will 
remain  suspended  at  a  height  of  twenty-eight  or 
thirty  inches.  If  there  be  placed  beside  Fig.  202 
the  tube  a  scale,  d,  divided  into  inches  and 
decimal  parts,  the  zero  of  the  division 
coinciding  with  the  level  of  the  mercury 
in  the  cup,  such  an  instrument  forms  the 
'c  barometer; 

The  cause  of  the  suspension  of  the  mercury  in 
the  tube  is  the  pressure  of  the  air.  This  may  be 
demonstrated  by  placing  over  the  barometer  a 
tall  air-pump  receiver,  and  exhausting.  It  will 
be  found  that,  as  the  pressure  in  the  interior  of 
the  receiver  is  reduced,  the  column  of  mercury 
in  the  barometer  falls,  and  on  restoring  the  press- 
ure it  rises  to  its  original  point. 

Fie.  203.  The  same  fact  may  be  proved  in  another  manner 
If  a  tube,  upward  of  thirty  inches  long,  the  upper 
extremity  of  which  is  closed  by  a  piece  of  bladder, 
be  filled  with  mercury  and  inverted  in  a  cup,  as 
shown  in  Fig.  203,  the  bladder  will  be  found  deep- 
ly depressed,  the  pressure  of  the  air  in  that  di- 
rection being  borne  by  it ;  but  if  now  a  minute  pin- 
hole  is  made  in  the  bladder,  so  as  to  allow  the  air 
to  press  upon  the  top  of  the  mercury,  the  column 
>rapidly  descends,  flowing  out  of  the  tube. 
The  barometer  was  originally  invented  by  Torricelli. 
Some  plumbers,  working  for  the  Duke  of  Florence,  found 
that  it  was  impossible  to  make  a  pump  which  should  raise 
water  more  than  about  thirty  feet.  This  fact  eventually  com- 
ing to  the  knowledge  of  Torricelli,  he  suspected  that  the 
water  rose  in  those  machines  in  consequence  of  the  pressure 
of  the  air,  and  not  through  Nature's  abhorrence  of  a  vac- 
uum, as  was  at  that  time  supposed.  But  if  the  limit  to 
which  water  can  be  raised  by  a  pump  is  reached  when  the 
pressure  of  the  column  of  liquid  equilibrates  the  pressure 
of  the  air,  it  follows  that  if  a  heavier  fluid  than  water  be 

Describe  the  barometer.  What  is  it  which  supports  the  mercurial  col» 
umn  ?  How  may  this  be  proved  ?  By  whom  was  the  barometer  invent 
ed?  What  were  the  circumstances  of  the  invention?  •» 


PRINCIPLE    OF    THE    BAROMETER.  201 

used,  the  height  to  which  it  can  be  raised  is  less.  A  pump 
ought,  therefore,  to  lift  quicksilver  only  about  as  many 
inches  as  it  can  lift  water  feet ;  for  the  weight  of  these 
liquids  is  about  as  one  to  thirteen  and  a  half,  and,  accord- 
ingly, Torricelli  found,  by  means  of  a  small  pump  fixed 
to  a  long  glass  tube,  that  such,  in  reality,  is  the  case.  The 
barometer  is  a  simplification  of  the  same  apparatus. 

That  it  is  the  pressure  of  the  air  which  sustains  the  mer- 
curial column  was  satisfactorily  proved  by  Paschal,  who 
reasoned  that,  if  this  were  the  case,  the  barometric  column 
ought  to  be  shorter  on  the  top  of  a  mountain  than  in  a 
valley,  because  in  the  former  position  that  pressure  must 
necessarily  be  less.  On  the  experiment  being  made,  hia 
reasoning  was  found  to  be  true. 

The  principle  of  the  barometer  may  be  illustrated  by 
substituting  for  the  pressure  of  air  the  pressure  of  a  col- 
umn of  water.  Thus,  if  we  pour  some  quicksilver  into 
the  bottom  of  a  deep  glass  jar,  a,  Fig.  204,  and 
plunge  into  it  a  long  tube,  b,  open  at  both  ends, 
the  quicksilver  will  rise  in  this  tube,  so  that  its 
level  on  the  inside  will  be  coincident  with  that  on 
the  outside.  But  if  now  we  begin  to  fill  the  jar 
with  water,  r,  for  every  thirteen  and  a  half  inches 
in  depth  poured  in,  the  quicksilver,  d,  will  rise 
one  inch,  the  mercurial  column  counterpoising 
the  column  of  water.  And,  on  the  same  princi- 
ple, the  column  of  quicksilver  in  the  barometer  counter- 
poises that  of  the  air  to  the  top  of  the  atmosphere. 

Mr.  Boyle  discovered  that  the  pressure  of  the  air  is  not 
always  the  same,  but  it  undergoes  many  variations,  the 
mercurial  column  sometimes  falling  near  to  27  inches,  or 
rising  above  30.  The  range  is  commonly  estimated  at 
2'5  inches.  It  is  considerably  less  in  the  tropics.  These 
changes  of  pressure  are  exceedingly  irregular,  and  are 
connected  with  meteorological  phenomena.  There  are 
also  diurnal  variations,  the  column  rising  twice  in  the 
twenty-four  hours.  In  winter  the  first  maximum  is  about 
nine  A.M.,  and  the  minimum  at  three  P.M.,  the  second 
maximum  being  about  nine  P.M. 

What  was  Paschal's  experiment  ?  What  did  it  prove  ?  How  may  the 
phenomena  of  the  barometer  be  illustrated  by  the  pressure  of  a  water 
column  ?  What  is  the  extent  of  the  irregular  variations  of  pressure  ?  What 
are  the  diurnal  variations  ?  At  what  times  do  the  maxima  and  minima 
occur  ? 


202  DIFFUSION    OF    GASES. 

It  has  already  been  observed  that  the  mean  pressure  of 
the  air  is  estimated  at  15  pounds  upon  a  square  inch,  or 
equal  to  a  column  30  inches  long.  A  man  of  average  size 
sustains  a  pressure  on  the  surface  of  his  body  of  nearly 
thirty  thousand  pounds. 

The  temperature  of  the  atmosphere  is  lower  as  we  as- 
cend to  more  elevated  regions.  A  point,  therefore,  can 
always  be  reached  over  any  place  of  which  the  tempera- 
ture never  rises  over  32°  F.,  and  where  water  is  always 
frozen.  This  point  is  known  under  the  name  of  the  point 
of  perpetual  congelation.  Its  altitude  differs  very  much 
in  different  places,  being  highest  at  the  equator,  and  low- 
er as  we  go  toward  the  poles.  It  is  at 

The  Equator.     .     .     .  15,000  feet. 
Latitude  40°  ....      9000    " 
"          75°  ....      1000    " 
85°  ....        117    " 

Many  causes  conspire  to  give  rise  to  local  disturbances 
in  the  constitution  of  the  air.  In  its  lower  strata  combus- 
tion and  respiration  are  actively  going  on ;  they  tend  to 
diminish  the  oxygen  and  increase  the  carbonic  acid.  At 
the  equator  the  effect  of  a  constantly  brilliant  sunshine  on 
the  leaves  of  plants  is  to  diminish  the  carbonic  acid  and 
increase  the  oxygen.  But  notwithstanding  these  local  dis- 
turbances, and  also  the  fact  that  the  constituents  of  the 
air  are  of  very  different  specific  gravities,  the  constitution 
of  the  atmosphere  is  nearly  the  same  in  all  places.  This 
Pig.  205.  commixture  is  partly  effected  by  the  mechanical 
action  of  winds,  and  partly  by  the  property  which 
gases  have  of  diffusing  into  each  other.  Thus, 
if  two  vials,  a  and  e,  Fig.  205,  communicate  with 
each  other  by  means  of  stop-cocks,  b  c  d,  and  if, 
in  a,  a  light  gas,  such  as  hydrogen,  is  placed,  and 
in  e  a  heavy  gas,  as  carbonic  acid,  in  a  few  min- 
utes after  the  stop-cocks  are  opened  the  gases 
will  diffuse  into  each  other,  the  light  one  descend- 
ing and  the  heavy  one  ascending,  until  they  are 
perfectly  commixed.  And  this  effect  will  take 
place  even  though  a  barrier  should  intervene. 
Thus,  Dr.  Mitchell  found  that  gases  would  read- 
ily pass  through  the  close  texture  of  India-rub- 

What  is  the  point  of  perpetual  congelation  ?  How  does  it  vary  with 
the  latitude  ?  What  are  the  causes  which  tend  to  change  the  composi- 
tion of  the  air  ?  What  is  meant  by  the  diffusion  -of  gaaes  ?  , 


MARRIOTTE'S    LAW.  203 

ber  to  mingle  with  each  other ;  and  I  have  observed  the 
same  in  the  case  of  films  of  water.  Thus,  if  a  Fi  206 
bottle,  a,  Fig.  206,  full  of  atmospheric  air,  have  its 
mouth  closed  by  a  film  of  soap-water  spread  over 
it  by  the  finger,  and  then  be  placed  under  a  bell 
jar  containing  protoxide  of  nitrogen,  this  latter 
gas  passes  rapidly  through  the  film,  and  distends 
it  into  a  bubble  by  forcing  its  way  into  the  bottle. 
The  force  with  which  gases  will  thus  pass  into  each  other 
is  sometimes  very  great.  I  have  proved  that  sulphureted 
hydrogen  will  diffuse  into  atmospheric  air,  though  resist- 
ed by  a  pressure  of  more  than  fifty  atmospheres. 

That  the  atmospheric  air  is  a  mixture,  and  not  a  com- 
pound, is  proved  by  its  easy  decomposibility,  its  refract- 
ive power,  and  by  the  fact  that  its  constituents  retain  their 
properties  unchanged.  The  amount  of  its  oxygen  may  be 
determined  by  the  combustion  of  phosphorus,  or  detona- 
tion with  hydrogen  ;  the  amount  of  its  carbonic  acid,  which 
varies  in  damp  or  dry  seasons,  being  dissolved  out  by 
showers  of  rain,  may  be  determined  by  potash  or  lime- 
water,  and  its  aqueous  vapor  by  the  process  for  the  dew- 
point  already  described. 

Atmospheric  air  being  thus  an  elastic  and  compressi- 
ble body,  it  remains  to  explain  the  law  which  de-  Fig.  207 
termines  its  volume  under  changes  of  pressure. 
This  is  known  under  the  name  of  the  law  of  Mar- 
riotte,  and,  applying  to  many  other  gases  besides 
atmospheric  air,  is  to  the  effect  that  the  tolume  of 
a  gas  is  inversely  as  the  pressure  upon  it.  This  law 
is  of  the  utmost  importance  in  gaseous  chpmistry. 
It  may  be  illustrated  by  the  instrument  (Fig.  207), 
where  a  b  is  a  bent  tube,  open  at  the  end  #,  and 
closed  at  b.  The  branch  a  may  be  several  feet 
long,  and  b  six  inches.  A  small  quantity  of  mercury  is 
poured  into  the  tube,  so  as  to  occupy  the  bend  and  shut 
up  a  column  of  air  between  d  and  b.  Now,  if  the  tube  ia 
filled  with  quicksilver  to  the  height  of  30  inches,  as  to  a, 
the  pressure  of  this  column  is  exerted  on  the  air  in  the 
closed  branch,  b  ;  and  as  there  are  now  the  weight  of  two 
atmospheres,  that  of  the  ordinary  atmosphere  and  that  of 

Does  this  take  place  through  intervening  barriers  ?  How  is  this  con- 
nected with  the  constitution  of  the  air  ?  What  proofs  are  there  that  the 
atmosphere  is  a  mixture,  and  not  a  compound  ?  What  is  Marriotte's  law  f 
How  may  its  truth  be  proved  ?  Giv«  examples  of  Marriotte's  law. 


204  DILATATION    OF    ATMOSPHERIC    AIR. 

the  mercurial  column,  it  is  compressed  into  half  its  former 
volume,  c.  If  we  bring  upon  it  three  atmospheres,  it  will 
be  compressed  into  one  third ;  if  four,  to  one  fourth,  &c. 
And  the  law  holds  good,  also,  for  diminutions  of  pressure. 
If,  on  a  given  volume  of  gas,  the  pressure  is  reduced  to 
one  half,  the  volume  doubles  ;  if  to  one  third,  it  triples  ; 
to  one  fourth,  it  quadruples  ;  in  all  cases  the  volume  being 
inversely  as  the  pressure. 

The  exact  amount  of  dilatation  of  atmospheric  air  for 
elevations  of  temperature  was  determined  by  G-ay-Lussac 
as  follows  :  In  a  tin  box,  A,  containing  water,  there  is  in- 


Fig.  208. 


troduced  through  a  perforation  at  o'  a  bulb,  g,  with  a  tube, 
g',  containing  the  air,  the  dilatation  of  which  is  to  be 
measured.  This  air  has  been  previously  introduced  in  a 
state  of  dryness  by  the  chloride  of  calcium  tube,  li  h1.  At 
m  is  a  globule  of  mercury,  which  acts  as  an  index,  and 
confines  the  air.  On  the  opposite  side  of  the  tin  box,  at 
o,  a  thermometer,  s  t  b,  is  introduced,  and  another  one,  v, 
passing  through  the  top  of  the  box,  occupies  the  center. 
The  bcx  is  first  filled  with  water  containing  fragments  of 
ice,  and  when  the  thermometers  are  at  32°,  the  position 
of  the  index,  m,  is  marked.  The  furnace  is  then  lighted, 
and  when  the  water  boils,  and  the  thermometers  are  at 
212°,  the  index,  m,  is  again  observed.  The  difference 
indicates  the  dilatation  of  the  air  for  180° ;  and  in  this 
manner  Gay-Lussac  found  that  1000  volumes  of  air  be- 
come 1375.  These  results  have  been  of  late  carefully  ex- 
amined by  Rudberg,  who  fixes  the  amount  of  expansion 
of  air  at  Tij  of  its  volume,  at  32°,  for  every  degree  of 
Fahrenheit's  scale. 


What  is  the  law  of  Gay-Lussac  ?    What  is  the  absolute  dilatation  of  air 
«£  determined  by  Rudberg  ? 


PROTOXIDE    OF    NITROGEN.  205 


LECTURE  XL\. 

COMPOUNDS  OP  NITROGEN  AND  OXYGEN. — Protoxide  oj 
Nitrogen. — Preparation  and  Properties  of. —  Constitu- 
tion.— Supports  Combustion. — Produces  Intoxication. 

Deutoxide  of  Nitrogen. — Preparation  and  Properties  of. 
—  Constitution. — Relations  to  free  Oxygen. — Hyponitric 
Acid. — Preparation  and  Properties  of. 

PROTOXIDE  OP  NITROGEN.    NO  =  22-203 
IF  the  nitrate  of  ammonia  be  exposed  to  a  temperature 
of  about  350  degrees  in  a  retort,  Fig.  209. 

Fig.  209,  it  undergoes  decompo- 
sition, being  resolved  into  water 
and  the  protoxide  of  nitrogen  ;  the 
former  condensing  in  the  neck  of 
the  retort,  and  the  latter  rising 
into  the  pneumatic  jar.  If  whitish 
fumes  are  evolved,  they  indicate  that  the  process  is  going 
on  too  fast,  and  the  heat  must  then  be  moderated.  The 
change  taking  place  is  very  simple.  It  is  a  mere  rearrange- 
ment of  the  constituent  atoms  of  the  nitrate  of  ammonia. 

NO,  +  NH3  ...  =  ...  2(NO)  +  3(HO). 
One   atom  of  that  salt,  therefore,  yields  two  atoms  of 
protoxide  of  nitrogen  and  three  of  water. 

The  protoxide  of  nitrogen  is  a  colorless  gas,  transpa- 
rent, like  atmospheric  air ;  it  has  a  sweetish  taste,  and  is 
soluble  in  water,  that  liquid  taking  up  about  three  fourths 
of  its  volume  of  the  gas  when  cold,  but  the  solvent  power 
being  greatly  diminished  by  warming  the  water.  Its 
specific  gravity  is  1-527.  It  may  be  liquefied  at  Fig_2W 
45°  by  a  pressure  of  fifty  atmospheres,  and  has 
even  been  solidified.  It  is  composed,  by  atom,  of 
one  of  nitrogen  and  one  of  oxygen,  and  by  vol- 
ume, of  two  volumes  of  nitrogen  united  to  one  of 
oxygen,  condensed  into  two  volumes,  a  constitution 
like  that  of  water.  It  therefore  contains  half  its 
bulk  of  oxygen  gas,  and  supports  combustion  with 

How  may  protoxide  of  nitrogen  be  made  ?    "What  are  its  properties  * 
What  is  its  constitution  ?    Does  it  support  combustion  ? 

S 


200  DEUTOXIDE    OF    NITROGEN. 

activity.  A  lighted  taper  immersed  in  it  burns  brightly, 
and,  as  in  oxygen,  if  there  be  merely  a  spark  on  the  wick, 
it  kindles  into  a  flame.  Phosphorus  burns  in  it  with  great, 
brilliancy. 

Sir  H.  Davy  discovered  that  not  only  does  this  gas  sup- 
port respiration,  but  that  it  exerts  a  remarkable  physio- 
logical action  when  breathed,  producing  a  transient  in- 
toxication, which  wears  off  after  two  or  three  minutes. 
These  effects  are  undoubtedly  due  to  the  oxydizing  ac- 
tion which  the  protoxide  establishes  in  the  system.  In 
this  respect  it  is  far  more  active  than  even  pure  oxygen 
gas,  and  the  reason  is  obvious  :  oxygen  is  but  slightly  ab- 
sorbable  by  watery  fluids,  but  this  gas  is  taken  up  by 
them  to  a  very  great  extent.  When  it  is  introduced  into 
the  lungs,  it  is  rapidly  dissolved  in  the  blood,  and  carried 
by  the  circulation  to  every  part  of  the  body,  oxydizing 
whatever  is  in  its  path,  and  producing  a  febrile  warmth 
and  an  unusual  mental  disturbance. 

The  protoxide  of  nitrogen  shows  but  little  disposition  to 
unite  with  other  bodies.  It  may  be  regarded  as  an  in- 
different substance. 

DEUTOXIDE  OF  NITROGEN.    NO2  =  30-216. 

The  deutoxide  or  binoxide  of  nitrogen  may  be  made 
by  the  action  of  nitric  acid  moderately  diluted  upon  me- 
tallic copper.  If  these  substances  are  introduced  into  a 
flask  together,  and,  when  the  action  mod- 
erates, fresh  portions  of  nitric  acid  be  added 
through  the  funnel  (Fig.  211),  a  colorless  gas 
is  evolved,  which  may  be  collected  over  wa- 
ter, in  which  it  is  only  sparingly  soluble,  one 
hundred  volumes  of  that  liquid  dissolving 
about  five  of  the  gas. 

It  is  composed  of  equal  volumes  of  nitrogen 
and  oxygen  united,  without  condensation.  Its  specific  grav- 
ity is,  therefore,  1"0416.  It  does  not  support  combustion  ; 
a  lighted  taper  immersed  in  it  is  at  once  extinguished  ; 
but  if  phosphorus,  burning  violently,  be  introduced  in  it, 
the  combustion  goes  on  with  increased  activity.  Iron 
and  several  other  metals  withdraw  from  it  one  half  of 
its  oxygen,  converting  it  into  the  protoxide. 

What  are  its  relations  to  respiration  ?  How  long  does  this  intoxicating 
effect  last  ?  What  is  the  cause  of  it  ?  Why  is  the  protoxide  of  nitrogen 
au  indifferent  substance  ?  How  is  the  deutoxide  obtained  ?  What  is  it« 
constitution  ?  Does  it  support  combustion  ? 


HYPONITBOU3    ACID.  20? 

The  most  remarkable  quality  of  the  deutoxide  of  nitro- 
gen is  its  action  on  mixtures  containing  oxygen  gas,  as, 
for  example,  atmospheric  air  ;  with  these  it  at  once  pro- 
duces red  fumes  of  nitrous  acid,  which  are  soon  removed 
if  water  be  present,  the  deutoxide  taking  up  two  atoms 
of  oxygen  to  change  into  nitrous  acid.  On  this  principle 
it  has  been  used  for  the  purpose  of  effecting  the  analysis 
of  atmospheric  air,  but,  unless  several  precautions  are  ob- 
served, the  results  are  incorrect.  The  deutoxide  should 
be  added  in  a  small  and  steady  stream  to  the  air  ;  red 
fumes  are  at  once  produced  ;  these  are  soon  removed  by 
the  water,  and  the  residue  is  less  in  volume  than  the  air 
and  deutoxide  taken  together.  One  fourth  of  the  deficit 
is  equal  to  the  volume  of  the  oxygen  originally  present. 
»By  operating  in  this  manner,  as  I  have  had  many  occa- 
sions to  observe,  correct  results  may  be  obtained.  The 
general  process  may  be  illustrated  by  taking  a  tall  jar 
and  placing  in  it  a  certain  volume  of  atmospheric  air,  to 
which-  is  to  be  added  an  equal  volume  of  the  deutoxide. 
Though  both  gases  are  colorless  at  first,  a  deep  copper- 
colored  vapor  is  the  result  ;  this  is  removed  after  a  time 
by  the  action  of  the  water,  which,  rising  in  the  jar,  ex- 
hibits a  deficit  in  the  amount  of  the  gases. 

A  solution  of  the  protosulpbate  of  iron  dissolves  this 
gas  abundantly  ;  and  if  a  small  quantity  of  the  sulphuret 
of  carbon  be  poured  into  it,  and  a  light  applied,  the  mix 
ture  burns  with  a  blue  flame. 

HYPONITllOUS  ACID.     NO3  —  38'229. 

This  substance'  may  be  made  by  mixing  four  volumes  of 
dry  deutoxide  of  nitrogen  with  one  of  dry  oxygen,  and 
exposing  the  mixture  to  cold.  The  gases  condense  into 
a  liquid  of  a  greenish  color,  which  gives  forth  an  orange 
vapor.  Hyponitrous  acid  is  decomposed  by  the  contact 
of  water,  deutoxide  of  nitrogen  escaping  with  an  effer- 
vescence, and  nitric  acid  being  produced,  three  atoms  of 
hyponitrous  acid  yielding  one  of  nitric  acid  and  two  of 
the  deutoxide. 


What  is  its  action  on  gaseous  mixtures  containing  oxygen  ?  -  Under 
what  circumstances  may  it  be  used  to  determine  the  amount  of  oxygen  ? 
How  may  its  action  on  oxygen  mixtures  be  illustrated  ?  What  is  its  re- 
lation with  the  protosulphate  of  iron?  And  what  with  the  vapor  of  sul- 
phuret of  carbon  ?  How  may  hypoiiitrous  acid  be  procured  ?  What  is 
the  action  of  water  on  it  ?  • 


208  NITROUS    ACID. 


LECTURE  XL VI. 

COMPOUNDS  OP  NITROGEN  AND  OXYGEN. — Nitrous  Acid. 
— Preparation  and  Properties  of. — Remarkable  Changes 
of  Color. —  Nitric  Acid. — Discovery  of. —  Cavendish's 
Experiments. — Sources  from  which  it  is  Derived. —  Com,' 
mercial  Preparation. — Its  Properties. — Is  a  Hypothet- 
ical Body. — Purification. — Detection . 

NITROUS  ACID.    NO4  =  46-242. 

NITROUS  acid  may  be  made  by  mixing  together  one 
volume  of  dry  oxygen  with  two  of  the  dry  deutoxide  of 
nitrogen,  and  exposing  the  mixture  to  a  very  low  tem- 
perature ;  but  it  is  much  more  easily  procured  by  distill- " 
ing,  in  a  porcelain  or  hard  glass  Fig.  212. 

retort,  a,  Fig.  212,  dry  nitrate  of 
lead,  and  receiving  the  gases  in 
a  tube,  I,  artificially  cooled  by  a 
freezing  mixture,  c.  The  nitrous 
acid  condenses  as  a  colorless  liquid, 
which  becomes  yellow  as  its  temperature  rises.  Its  spe- 
cific gravity,  in  the  liquid  form,  is  1/42.  It  solidifies  at 
40°  F.,  and  boils  at  82°  F.  Its  vapor  possesses  remark- 
able optical  qualities.  When  its  temperature  is  very  low, 
it  is  nearly  colorless ;  it  takes  on  an  orange  tint  as  the 
degree  of  heat  increases,  and  finally  becomes  almost 
black.  The  peculiarity  of  the  phenomenon  is,  that  if  the 
gas  be  examined  while  undergoing  these  changes,  by 
passing  a  ray  of  light  through  it  and  analyzing  it  by  means 
of  a  prism,  as  explained  in  Lecture  XIX.,  a  great  number 
of  fixed  lines  are  found  in  the  resulting  spectrum  ;  and  as 
the  temperature  rises  these  increase  so  much  in  number 
and  in  breadth  that  the  light  becomes  finally  obliterated. 

The  vapor  of  nitrous  acid,  when  once  mixed  with  atmos- 
pheric air,  is  condensed  into  the  liquid  form  with  great 
difficulty.  It  is  wholly  irrespirable,  and,  even  when  di- 
luted, of  a  very  unpleasant  odor.  Nitrous  acid  is,  for  the 
most  part,  decomposed  by  water, 

)4  ...  =  ...  2NO&  +  NOt, 


How  may  nitrous  acid  be  made  ?  What  are  its  properties  ?  How  does 
the  color  of  its  vapor  change  by  heat  ?  What  is  the  cause  of  the  fina. 
blackness  ?  What  are  the%elations  of  nitrous  acid  and  water? 


NITRIC    ACID.  209 

three  atoms  of  it  yielding  to  two  of  nitric  acid  and  one  of 
the  deutoxide  of  nitrogen,  as  seen  in  the  formula ;  but 
the  nitric  acid  produced  protects  a  portion  of  the  nitrous 
acid,  which  thus  escapes  decomposition.  Its  vapor  is  ab- 
sorbed by  nitric  acid.  The  production  of  this  acid  by  the 
process  with  nitrate  of  lead  is  of  considerable  philosoph 
ical  interest ; 

PbO  +  NO,  ...  =  ...  PbO  +  NO,  +  O, 

one  atom  of  the  nitrate  of  lead  yielding  one  atom  of  ox 
ide  of  lead,  which  remains  in  the  retort,  one  of  nitrous 
acid,  and  one  of  oxygen  gas,  which  escape.  It  might  be 
expected  that,  in  such  a  distillation,  we  should  obtain 
oxide  of  lead  and  nitric  acid.  The  cause  of  the  non-ap- 
pearance of  the  latter  body  will,  however,  be  presently 
understood. 

NITRIC  ACID.    NOs  —  54-255. 

Nitric  acid,  the*  most  important  of  the  compounds  of 
oxygen  and  nitrogen,  and  one  of  the  most  important  of 
the  acid  bodies,  was  first  discovered  during  the  ninth 
century.  The  discovery  of  this  and  some  of  the  other 
powerful  acids  form  one  of  the  epochs  in  chemistry.  The 
science  can  scarcely  be  said  to  have  existed  until  that 
time,  the  Egyptians,  Greeks,  and  Romans  having  no 
knowledge  of  these  bodies,  nor,  indeed,  of  any  more  pow- 
erful than  vinegar. 

The  constitution  of  nitric  acid  was  determined  by  Mr. 
Cavendish,  who  formed  it  synthetically,  by  passing  electric 
sparks  through  atmospheric  air  in  contact  with  a  solution 
of  potash.  The  nitrate  of  potash  was  obtained. 

Nitric  acid  also  occurs  to  a  small  extent  in  rain  water, 
especially  after  thunder  storms,  and  by  some  supposed  to 
originate  upon  the  same  principles  as  in  Cavendish's  ex- 
periments ;  but  probably  it  is  due  to  the  oxydation  of 
ammonia,  which  always  exists  in  the  air.  The  chief  sup- 
ply is  derived  indirectly  from  the  decay  of  vegetable  or 
animal  matter,  in  the  presence  of  oxygen  gas,  and  in  con- 
tact with  basic  bodies.  Collections  of  such  refuse  pass 
under  the  name  of  nitre  beds,  and,  in  France  and  Ger- 

What  is  the  decomposition  whtfch  takes  place  when  nitrate  of  lead  is 
distilled?  When  was  nitric  acid  discovered?  How  was  its  composition 
determined  by  Cavendish  ?  What  is  the  source  of  the  nitric  acid  in  rain 
water? 

S2 


210 


NITRIC    ACID. 


many,  furnish  the  saltpetre  which  is  used  for  the  manu- 
facture of  gunpowder.  In  the  East  Indies,  nitrate  of 
potash  is  obtained  by  lixiviation  from  the  soil  in  which 
earthy  nitrates  naturally  occur.  From  South  America 
the  nitrate  of  soda  is  exported  ;  it  is  found  as  an  efflo- 
rescence on  sails  in  which  common  salt  probably  exists. 

In  most  of  these  cases  the  nitric  acid  arises  from  the 
oxydation  of  ammonia  produced  during  putrefactive  fer- 
mentation. 

NH3  +  08  ...  =  ...  NO,  +  3HO. 

The  formula  shows  the  probable  nature  of  the  action  ;  one 
atom  of  ammonia,  under  the  influence  of  eight  of  oxygen, 
will  yield  one  of  nitric  acid  and  three  of  water. 

The  nitric  acid  of  commerce  is  made  by  distilling  equal 
weights  of  sulphuric  acid  and  nitrate  of  potash.  The 
process  may  be  conducted  in  a  small  way  in  a  glass  re- 
tort, A,  Fig.  213  ;  and  it  is  found  advantageous  to  use 

Fig.  213. 


the  quantity  of  sulphuric  acid  here  stated,  because  a  solu- 
ble bisulphate  of  potash  is  formed,  which  may  be  easily 
removed  without  breaking  the  retort.  Half  as  much  sul- 
phuric acid  would  effect  the  decomposition,  but  it  would 
•require  a  higher  temperature,  and  the  neutral  sulphate 
which  forms  could  with  difficulty  be  removed.  The 
change  which  takes  place  is  thus  exhibited  : 

(KO,  M)5)  +  2(HO,  SO,}  ...  =  ..  ..(KO,  HO,  2SO3) 


From  what  sources  is  nitrate  of  potash  produced  ?     How  may  nitric  acid 
ise  from  the  oxydation  of  ammonia  ?     How  may  nitric  acid  be  made  1 


PROPERTIES   OF    NITRIC    ACID.  211 

that  is,  one  atom  of  nitrate  of  potash  and  two  of  sulphuric 
acid  furnish  one  atom  of  bisulphate  of  potash,  and  one  of 
hydrated  nitric  acid  distills  over  into  the  receiver,  B,  which 
is  kept  cool  by  a  stream  of  water  flowing  from  i  into  a 
vessel,  c  c,  the  waste  water  passing  through  led.  A  net 
is  wrapped  over  the  receiver  to  distribute  the  water 
evenly.  In  this  process  nitrate  of  soda  may  be  advanta- 
geously substituted  for  nitrate  of  potash. 

Hydrated  nitric  acid  thus  produced  is  a  colorless  liquid, 
which  boils  at  248°  F.,  though  this  point  changes  with 
the  amount  of  water  in  the  acid.  It  freezes  at  —  40°  ;  is 
decomposed  into  oxygen  and  nitrogen  by  being  passed 
through  a  red-hot  glass  tube.  It  turns  yellow  in  the  sun- 
shine, owing  to  a  portion  being  decomposed  and  nitrous 
acid  set  free,  which  dissolves  in  the  residue,  and  gives  it 
an  orange  tint.  The  nitric  acid  of  the  shops  (aqua  fortis) 
commonly  possesses  this  color,  from  which  it  may  be 
freed  by  boiling  in  a  glass  vessel.  It  stains  the  skin  and 
other  organic  matters  yellow,  and  hence  is  used  in  the 
arts  of  dyeing.  Its  action  on  many  metalline  and  other 
combustible  bodies  is  exceedingly  violent,  ow-  Fig.  214. 
ing  to  the  great  amount  of  oxygen  it  contains. 
Poured  upon  some  pieces  of  copper  in  a  wine- 
glass, over  which  a  bell  jar  may  be  inverted 
(Fig.  214),  an  effervescence  takes  place,  and 
the  red  fumes  of  nitrous  acid  abundantly  form. 
Though  it  is  one  of  the  most  powerful  oxydizing 
agents  we  possess,  it  often  happens  that,  in  a  state  of 
great  concentration,  it  will  scarcely  act  on  a  metal,  but 
the  addition  of  a  little  water  causes  the  action  to  set  in. 

Nitric  acid  (iVO5)  is  a  hypothetical  or  imaginary  body 
which  has  never  yet  been  isolated  ;  the  nearest  approach 
to  it  that  we  know  is  the  strongest  aqua  fortis.  This  has 
a  specific  gravity  of  1-521,  and  consists  of  one  atom  of 
hypothetical  nitric  acid  and  one  of  water.  Its  formula, 
therefore,  is 

NO.  +  HO. 
Its  molecular  constitution  probably  is 


What  are  its  properties  ?  When  passed  through  a  red-hot  tube,  what 
happens  to  it  1  Why  is  commercial  nitric  acid  often  yellow  ?  -What  is  the 
action  of  this  acid  on  the  skin  and  on  metallic  bodies  ?  What  is  the  near- 
est approach  to  hypothetical  nitric  acid  ? 


212  SULPHUR. 

It  is,  as  we  shall  find  hereafter,  a  hydrogen  acid.  From 
this  we  see  the  reason  of  the  circumstance  that  in  the  de- 
composition of  dry  nitrate  of  lead,  described  in  this  Lecture, 
nitric  acid  does  not  make  its  appearance,  but  nitrous  acid 
and  oxygen  ;  for,  being  a  hypothetical  body,  its  atom  is 
dissevered  in  the  act  of  being  set  free. 

Nitric  acid  of  commerce  can  be  purified  by  distillation, 
rejecting  the  first  portions  which  come  over,  as  they  con 
tain  chlorine,  and  leaving  a  portion  in  the  retort  contain- 
ing sulphuric  acid  and  fixed  impurities.  If  twelve  parts 
are  distilled,  the  first  three  may  be  cast  aside,  and  one 
left  in  the  retort;  the  intermediate  eight  are  pure. 

When  it  is  in  a  solution,  nitric  acid  may  be  detected  by 
the  addition  of  sulphuric  acid,  and  a  drop  or  two  of  pro- 
tosulphate  of  iron ;  a  brownish  color  is  produced  where 
the  two  liquids  meet.  When  in  a  concentrated  state,  the 
evolution  of  red  fumes,  by  the  action  of  copper,  detects 
it.  It  also  gives  a  blood-red  color  with  morphia.  The 
nitrates  deflagrate  when  ignited  with  combustible  matter, 
a  result  which  may  be  well  shown  by  grinding  together  a 
few  ounces  of  nitrate  of  potash  and  common  sugar,  and  set- 
ting fire  to  the  mixture.  Owing  to  the  solubility  of  all  its 
compounds,  nitric  acid  can  not  be  precipitated. 


LECTURE  XL VII. 

SULPHUR. — Natural  and  Artificial  Forms. — Preparation 
of  Flowers. — Properties  of  Sulphur. — Its  Vapor. — Ox- 
ygen Compounds  of  Sulphur. — Sulphurous  Acid. — Prep' 
aration.  —  Properties.  —  Bleaching  Effects. — Condensa~ 
tion  to  the  Liquid  State. — Its  Compounds. 

SULPHUR.     5  =  16-12. 

MUCH  of  the  sulphur  in  commerce  is  derived  from  vol- 
canic countries,  in  which  it  occurs  often  in  a  pure  and 
crystallized  state.  It  is  one  of  the  most  common  element- 
ary substances,  being  found  abundantly  united  with  va- 
rious metals,  such  as  iron,  copper,  lead.  In  combination 
with  lime,  baryta,  &c.,  it  occurs  as  sulphuric  acid,  and  is 

Why  can  not  it  be  isolated  ?  How  may  it  be  purified  ?  How  may  it 
be  detected  ?  Why  can  not  nitric  acid  be  detected  by  precipitation  ?  Un- 
der what  forms  does  sulphur  naturally  occur  ' 


FLOWERS    OF    SULPHUR. 


218 


also  an  ingredient  of  many  animal  and  vegetable  prod- 
ucts. 

Sulphur  is  met  with  under  three  different  forms  :  roll 
sulphur,  flowers  of  sulphur,  and  lac  sulphuris.  Roll  sul- 
phur is  an  impure  variety,  which  receives  its  form  from 
being  cast  into  cylindrical  molds  ;  the  flowers  of  sulphur 
are  formed  from  the  impure  brimstone  by  sublimation  ; 
lac  sulphuris  differs  from  the  foregoing  in  being  of  a  white 
color.  It  is  prepared  by  precipitation  from  the  persulphu- 
ret  of  potassium  by  hydrochloric  acid. 

The  preparation  of  flowers  of  sulphur  is  conducted  in 
an  apparatus,  such  as  Fig.  215.  A  is  a  room,  or  chamber, 


of  2000  feet  capacity ;  c  is  a  pan  containing  sulphur,  which 
is  melted  by  the  furnace,  o  s  ;  the  vapor  passes  along  i  d 
b,  and,  entering  the  chamber,  is  there  condensed.  The  re- 
sulting flowers  are  removed  through  the  door  p.  If  an 
explosion  occurs,  when  the  process  commences,  it  lifts 
the  valve  e,  and  the  gases  escape  through  the  chimney,  tt 
M  M  is  a  shed  under  which  the  apparatus  is  constructed. 
As  the  iron  pan  becomes  exhausted,  new  quantities  of 
brimstone  can  be  introduced  through  the  door  n. 

Sulphur  commonly  exists  as  a  solid  of  a  yellow  col- 
or, and  of  a  specific  gravity  of  1'99,  having  neither  taste 
nor  smell.  It  melts  at  226°  F.  into  a  pale  yellow-colored 
liquid ;  but  what  is  very  curious,  if  the  heat  be  raised  to 
about  450°  F.,  it  changes  to  the  color  of  molasses,  and  be 
comes  so  thick  and  tenacious  that  the  capsule  in  which 
the  fusion  is  carried  on  may  be  turned  upside  down  with- 
out the  sulphur  flowing  out.  At  600°  F.  it  boils,  and,  as 

What  are  its  artificial  forms  ?  How  are  the  flowers  of  sulphur  made  ? 
"What  are  the  properties  of  sulphur  ?  What  changes  may  be  observed  in 
it  when  melting'  ? 


PROPERTIES    OF    SULPHUR. 

the  heat  approaches  that  point,  it  again  becomes  fluid  ; 
and,  as  it  cools,  runs  through  the  same  changes  again  in  a 
reverse  order.  If  suddenly  quenched  in  cold  water  at  the 
low  temperature,  before  it  thickens,  it  solidifies  into  ordi- 
nary sulphur ;  but  if  heated  for  a  time  to  near  600°,  and 
then  quenched,  it  becomes,  on  cooling,  elastic,  like  India- 
rubber,  and  may  be  drawn  into  long  threads  ;  and  in  this 
state  is  sometimes  used  for  taking  casts  of  coins,  for  by 
keeping  a  few  days  it  slowly  returns  to  the  condition  of 
ordinary  sulphur. 

When  rubbed 'on  a  piece  of  flannel  it  becomes  highly 
electric,  assuming  the  negative  state,  and  at  one  time  was 
used  in  the  making  of  electrical  machines,  before  the  pow- 
ers of  glass  were  discovered.  A  roll  of  it  held  in  the 
warm  hand  emits  a  crackling  sound,  the  crystals  of  which 
it  is  composed  separating  from  one  another.  It  is  -a  bad 
conductor  of  heat  and  electricity,  crystallizes  under  two 
different  systems,  and  is,  therefore,  a  dimorphous  body, 
one  of  its  forms  being  an  acute  rhombic  octahedron,  and 
the  other  an  oblique  rhombic  prism.  When  heated  to 
about  300°  F.  in  the  open  air,  it  takes  fire,  and  burns 
witfi  a  blue  flame,  emitting  a  suffocating  odor,  fumes  of 
sulphurous  acid  gas.  It  is  wholly  insoluble  in  water ;  its 
proper  solvent  fe  the  bisulphuret  of  carbon. 

The  vapor  of  sulphur  is  of  a  deep  yellow  color,  and  has 
the  high  specific  gravity  of  6*648.  In  it  metallic  bodies 

will  burn  precisely  as  they  do 
Fig.  216.  ^  rf£^  *n  oxvgen  gas-  Dr.  Hare  has 
shown  that  if  a  gun  barrel  be 
heated  red  hot  at  the  breech, 
and  a  piece  of  sulphur  drop- 
ped into  it,  the  muzzle  being 
closed  with  a  cork,  an  ignited 
jet  of  sulphur  vapor  issues  from  the  touch-hole,  in  which, 
if  a  bunch  of  iron  wire  be  held,  it  takes  fire  and  burns  brill- 
iantly. 

.  Sulphur  has  a  very  extensive  range  of  affinities,  uniting 
with  most  metallic  substances  in  several  different  propor- 
tions, with  hydrogen  and  also  with  oxygen.  With  the 
latter  substance  it  furnishes  the  following  compounds : 

"What  electrical  condition  does  it  assume  by  friction  ?  What  are  its 
conducting;  powers  ?  Why  is  it  called  a  dimorphous  body  ?  At  what  tem- 
perature does  it  take  fire,  and  •what  is  the  product  of  its  combustion? 
What  is  the  specific  gravity  of  its  vapor?  Docs  it  support  combustion? 
What  are  the  oxygen  compounds  of  sulphur? 


SULPHUROUS    ACID. 


215 


SO3  .  .  SO3  .  . 


SZO5  . 


O 


6  ; 


Fig.  217. 


their  designations  are,  respectively, 

Sulphurous  acid. 

Sulphuric  acid. 

Hyposulphurous  acid. 

Hyposulphuric  acid. 

Sulphureted  hyposulphuric  acid  (acid  of  Langlois). 

Bisulphureted  hyposulphuric  acid  (acid  of  Fordos  and  Gelis). 

SULPHUROUS  ACID.     SO*  =  32-146. 

This  acid  may  be  formed  by  burning  sul- 
phur  in  oxygen  gas  or  in  atmospheric  air  ;  in 
the  latter  instance  the  resulting  gas  is,  ojf 
course,  contaminated  with  nitrogen.  The  pro- 
cess may  be  conducted  under  a  bell  jar,  the 
burning  sulphur  being  placed  on  a  capsule  or 
stand. 

But  a  much  better  process  is  to  effect  the 
partial  deoxydation  of  sulphuric  acid  by  heat- 
ing oil  of  vitriol  with  mercury,  which  deprives  it  of  one 
atom  of  oxygen,  forming  an  oxide  of  mercury,  which 
unites  with  one  atom  of  the  excess  of  .sulphuric  acid  pres- 
ent to  form  a  sulphate.  For  many  of  the  ordinary  purpo- 
ses to  which  sulphurous  acid  is  applied,  it  may  be  pro- 
cured by  the  action  of  fragments  of  charcoal  heated  with 
sulphuric  acid.  In  this  case,  however,  carbonic  acid  is 
also  evolved.  When*  a  solution  in  water  is  required,  the 
gas  may  be  passed  directly  into  that  liquid,  but  if  it  be  nec- 
essary to  retain  it  in  a  gaseous  state,  it  must  be  received 
in  jars  at  the  mercurial  trough,  or  collected  by  the  meth- 
od of  displacement. 

It  is,  under  ordinary  circumstances,  a  transparent  and 
colorless  gas,  having  an  un- 
pleasant  taste,  and  the  smell 
characteristic  of  burning  sul- 
phur. It  is  wholly  irrespira- 
ble,  and  promptly  extinguish- 
es a  lighted  taper.  Its  specific 
gravity  is  2'222,  and,  therefore, 
if  a  stream  of  it  which  has  been 
cooled  by  flowing  from  the 

How  may  sulphurous  acid  be  made  ?  What  is  the  principle  of  the  pro- 
cess when  sulphuric  acid  acts  on  mercury  or  charcoal?  What  are  tha 
products  in  each  case  ?  Why  must  the  gas  be  collected  over  mercury  ? 
What  are  its  properties  ? 


Fig.  218. 


216  SULPHUROUS    ACID. 

generating  flask  a,  Fig.  218,  through  a  bent  tube,  b,  immers- 
ed in  a  jar  of  cold  water,  be  conducted  to  the  bottom  of  an- 
other jar,  c,  the  gas,  as  it  collects,  displaces  the  atmospheric 
air,  floating  it  out  of  the  vessel.  This  process  is  of  very 
general  application  in  the  collection  of  gases  which  are 
absorbable  by  water,  and  is  known  under  the  name  of  the 
method  by  displacement. 

In  a  jar  of  sulphurous  acid  thus  collected,  if  a  lighted 
219-  taper  be  immersed,  it  is  at  once  extinguished. 
If  the  jar  be  inverted  over  water,  the  gas  is 
speedily  dissolved,  that  liquid  taking  up  about 
thirty-seven  times  its  volume  of  the  gas.  If  veg- 
etable colors  are  submitted  to  its  influence,  they 
are  bleached,  but  the  color  is  not  destroyed  as  in 
bleaching  by  chlorine,  since  it  can  be  restored 
by  the  action  of  a  stronger  acid. 
Sulphurous  acid  is  among  the  gases  one  that  most  read- 
ily takes  the  liquid  form.  If  there  be  connected  with  the 
flask  from  which  this  gas  is  being  evolved  a  bent  tube  pass- 
ing through  iced  water  in  ajar,  and  the  gas,  after  traversing 
this  tube,  be  conducted  into  a  bottle  placed  in  a  freezing 
mixture  of  snow  and  dilute  nitric  acid,  it  condenses  into 
a  colorless  fluid  of  the  specific  gravity  1'45,  which  boils 
at  14°  F.  This  fluid  is  sometimes  used  to  produce  in- 
tense cold  by  its  evaporation. 

With  bases,  this  acid  forms  a  complete  series  of  salts, 
the  sulphites,  which  are  readily  decomposed  by  the  stron- 
ger acids,  and  are  occasionally  employed  as  deoxydizing 
agents,  from  the  circumstance  that  metallic  oxides  maybe 
reduced  by  them,  their  sulphurous  passing  into  the  con- 
dition of  sulphuric  acid* 

What  is  the  method  by  displacement  ?  To  what  extent  is  this  acid  sol- 
uble in  water  ?  Are  its  bleaching  effects  permanent  ?  How  may  it  bo 
condensed  ?  What  are  the  properties  of  this  liquid  ?  For  what  purposes 
are  the  sulphites  employed  1 


SULPHURIC   ACID. 


217 


LECTURE  XLVIII. 

COMPOUNDS  OF  SULPHUR  AND  OXYGEN. — Sulphuric  Acid. 
—  The  Anhydrous  Acid. — Its  Affinity  for  Water. — Ger- 
man Oil  of  Vitriol. — Its  Constitution  and  Uses. — Com- 
mon Sulphuric  Acid. — Preparation  on  the  Large  Scale. 
— Its  C/iemical  Relations. — Purification. — Detection. — 
Other  Sulphur  Acids. 

SULPHURIC  ACID.    SO3  =  40-159. 

THIS  compound  is  not  alone  the  most  important  of  the 
acids  of  sulphur,  but  also  the  most  important  of  all  acids. 
By  the  aid  of  it,  nitric,  hydrochloric,  and  many  other 
strong  acids  are  made  for  commercial  purposes.  In  the 
production  of  carbonate  of  soda  and  chloride  of  lime,  im- 
mense quantities  of  it  are  consumed. 

Of  sulphuric  acid  we  have  several  varieties,  differing 
from  each  other  in  the  amount  of  water  they  contain. 
1st.  There  is  anhydrous  sulphuric  acid,  the  formula  for 
which  has  already  been  given  as  containing  one  atom  of 
sulphur  and  three  of  oxygen.  This  substance  may  be 
prepared  by  submitting  the  fuming  oil  of  vitriol  of  Nord- 
hausen  to  a  temperature  of  about  290°  Fahr.,  when  there 
distills  over  a  white  substance  of  a  crystalline  aspect.  It 
fumes  in  the  air,  melts  at  77°  Fahr.,  is  converted  into  va- 
por at  160°,  has  an  intense  affinity  for  water,  in  which,  if 
it  be  placed,  it  hisses  like  a  red-hot  iron.  It  is  to  be  par- 
ticularly remarked,  however,  that  the  acid  powers  of  this 
substance  are  very  feebly  marked  ;  it  shows  little  tenden- 
cy to  unite  with  other  bodies,  and  when  such  combina- 
tions are  effected,  the  resulting  substances  are  different 
from  the  true  sulphates. 

2d.  German,  or  Nordhausen  oil  of  vitriol,  HO,  SO3  -{- 
SO.. 

This  substance  is  prepared  by  taking  green  vitriol,  and, 
by  exposure  to  heat,  driving  off  its  water  of  crystalliza- 
tion (six  atoms),  and  also  a  portion  of  its  saline  water.  If 
the  dried  powder  be  placed  in  a  stone- ware  retort  and 
exposed  to  a  high  temperature,  there  distills  over  a  dark 

What  are  the  properties  of  anhydrous  sulphuric  acid,  and  how  is  it  pre- 
pared ?  W  hat  is  the  process  for  preparing  the  German  oil  of  vitriol  ? 
What  is  its  appearance  1 


218  OIL    OF    VITRIOL. 

oily  liquid ;  hence  the  term  oil  of  vitriol :  this  is  the  sub- 
stance in  question.  Its  formula  shows  that  it  is  composed 
of  two  atoms  of  anhydrous  acid  united  to  one  of  water. 
A  considerable  quantity  of  it  is  used  in  the  arts  /or  dis- 
solving indigo. 

3d.  Common  sulphuric  acid,  HO,  SO3. 
This  is  the  substance  which  passes  in  commerce  as 
common  oil  of  vitriol.  It  is  made  on  the  large  scale  by 
burning  sulphur  with  nitrate  of  potash  or  soda,  and  con- 
ducting the  sulphurous  and  nitrous  acids  which  result 
into  large  chambers  lined  with  lead,  in  which  steam  is 
thrown,  the  bottom  of  the  chamber  being  covered  with 
water.  The  sulphurous  acid  takes  oxygen  from  the  ni- 
trous acid,  reducing  it  to  the  condition  of  deutoxide ;  but 
this  being  done  in  the  presence  of  atmospheric  air,  which 
fills  the  chamber,  the  deutoxide  instantly  reassumes  the 
condition  of  nitrous  acid.  The  deutoxide,  therefore,  con- 
tinually transfers  oxygen  from  the  atmospheric  air  to  the 
sulphurous  acid,  and  brings  it  to  the  condition  of  sulphuric 
acid. 

After  a  time  the  water  at  the  bottom  of  the  chamber 
becomes  charged  with  sulphuric  acid ;  it  is  then  concen- 
trated by  drawing  off  the  excess  of  water  in  platina  or  glass 
boilers,  and  finally  assumes  the  specific  gravity  1'845.  It  is 
a  dense,  oily  liquid,  freezes  at  — 45°  and  boils  at  620°. 

The  attraction  of  common  sulphuric  acid  for  water  is 
F*£-.220.  very  intense.  If  a  tube,  containing  some  ether, 
be  stirred  in  a  glass  (Fig.  220)  in  which  sulphur- 
ic acid  and  water  are  being  mixed,  the  tem- 
perature rises  so  high  that  in  a  few  moments  the 
\a  ether  boils.  On  the  same  principle,  it  will  re- 
move from  most  gases  which  are  passed  over  it 
any  water  they  may  contain;  and,  as  we  have  seen 
in  Lect.  XII.,  water  may  be  frozen  by  taking  advantage 
of  the  rapidity  with  which  sulphuric  acid  will  absorb  its 
vapor.  Organic  substances  may  also  be  charred  by  the 
action  of  this  acid ;  for  example,  woody  fibre  is  a  com- 
pound of  carbon  with  the  elements  of  water,  and  when 
acted  upon  by  sulphuric  acid,  the  carbon  is  set  free,  the 
acid  taking  from  it  a  portion  of  its  water. 

For  what  purpose  is  it  used  ?  What  is  the  process  for  preparing  com- 
mercial sulphuric  acid?  What  are  its  properties?  What  illustration* 
may  be  given  of  its  intense  affinity  for  water  ? 


AC1D3    OF    SULPHUR.  219 

Sulphuric  acid  of  commerce  is  never  pure  ;  it  contains 
sulphate  of  lead,  derived  in  the  process  of  its  manufacture, 
and  also,  sometimes,  arsenic,  selenium,  and  nitrous  acid. 
From  the  first  it  may  be  purified  by  dilution  with  water,  in 
which  sulphate  of  lead  is  insoluble ;  but  when  required 
entirely  pure,  it  must  be  distilled,  the  first  portions  being 
rejected. 

The  presence  of  sulphuric  acid  may  be  detected  by  any 
of  the  soluble  salts  of  barium,  such  as  the  chloride  of 
barium,  or  the  nitrate  of  baryta,  the  white  sulphate  of 
baryta  precipitating  insoluble  in  water  and  acids. 

To  black  woolen  clothing  this  acid  communicates  a 
1  eddish  stain,  removable  by  being  touched  with  ammonia. 

Besides  the  compounds  just  described,  we  have  other 
definite  hydrates  of  sulphuric  acid,  thus  : 

(4)  S03  +  2HO. 

(5)  SO,  +  3HO. 

The  fourth  of  these  has  a  specific  gravity  of  1'78,  and 
crystallizes  at  39°  Fahrenheit  in  large  and  beautiful  crys- 
tals. The  fifth  has  a  specific  gravity  of  T632. 

HYPO-SULPHUROUS  ACID,  SaO2  =  48-266, 

has  not  yet  been  isolated ;  one  of  its  salts,  the  hyposul- 
phite of  soda,  is  extensively  used  in  the  Daguerreotype 
process  for  removing  the  sensitive  coating  on  the  plates. 

HYPOSULPHUBIC  ACID,  S2  O5  =  72-355, 

is  a  sirupy  liquid  of  a  very  acid  taste,  and  is  not  applied 
to  any  use. 

Besides  these,  we  have  two  other  acids  of  sulphur : 

Sulphureted  hyposulphuric  acid,  S3O5=  88-475,  discovered  by  Langloia. 
Bisulphureted  hyposulphuric  acid,  S*Oo  =  104-595,  discovered  by  Fordos 
and  G-elis. 

Chemists  are  now  very  generally  agreed  that  all  these 
compounds  are  to  be  regarded  as  hydrogen  acids — a 
striking  departure  from  the  Lavoisierian  doctrines.  They 
have  been  led  to  this  view  by  the  consideration  that  no 
well-marked  acid  exists  in  which  hydrogen  is  not  found  ; 
that  all  these  sulphur  acids  possess  the  same  neutralizing 

By  -what  substances  is  it  usually  rendered  impure  ?  How  may  it  be 
purified?  How  may  it  be  detected?  How  may  sulphuric  acid  stains  on 
clothing  be  removed?  What  other  hydrates  of  this  body  are  there? 
What  are  the  uses  of  hyposulphurous  acid  ?  What  other  sulphur  acida 
are  there  ?  What  is  the  nature  of  the  views  now  held  in  relation  to  the 
acida  of  sulphur,  and  acids  generally. 


220  SULPHURETED    HYDROGEN. 

power,  though  the  quantity  of  oxygen  they  contain  is  so 
different.  They  regard  them  all  as  being  formed  by  the 
union  of  one  atom  of  hydrogen  with  a  series  of  different 
compound  radicals,  as  the  following  table  shows  : 

Sulphurous  acid H4-  SO3. 

Sulphuric  acid     . H+  SO3  -f-  O. 

Hyposulphurous  acid H~{~  &O3  --  S. 

Hyposulphuric  acid //-}-  SO3  4-  SO3. 

Acid  of  Langlois H-\-  SO3  --  SO3  -4-S. 

Acid  of  Fordos  and  Gelis     .     .     .  H+  SO3  -f  SO3  +  S2. 

Chlorosulphuric  acid J7-f-  SO3  4-  Cl. 

Nitrosulphuric  acid H-\-  SO3  --  NO2. 

lodosulphuric  acid H--SO3-\-I; 

and,  extending  these  views  to  the  constitution  of  othei 
acids  generally,  an  acid  is  defined  to  be  "  a  compound  of 
hydrogen  with  a  simple  or  compound  radical,  in  which  the 
hydrogen  may  be  replaced  by  any  other  metal." 


LECTURE  XLIX. 

SULPHUR  AND  PHOSPHORUS. — Sulphureted  Hydrogen. — 
Mode  of  Preparing  it. — Its  Odor,  Acid  Relations,  and 
other  Properties. — Extensively  used  as  a  Test. —  Occurs 
in  Nature. — Relations  to  the  Animal  System. — Bisul- 
phureted  Hydrogen. — SELENIUM. — PHOSPHORUS. — Pre- 
pared from  Bones. — Shines  in  the  Dark. — Action  of 
Light. — Combustibility. —  Compounds  with  Oxygen 

SULPHURETED  HYDROGEX.    #£=17-12. 
Fig.  221.  THIS  gas  may  be  easily  prepared  by  the  ac- 

tion of  hot  hydrochloric  acid  on  the  native 
sulphtiret  of  antimony  pulverized,  and  may 
be  collected  over  a  saturated  solution  of  salt 
or  warm  water.  The  action  of  the  materials 
being 

Sb2S3  +  3(HCZ)  ...  =  ...Sb.2Cl3  +  3(HS) ; 
that  is,  one  atom  of  the  sesquisulphuret  of 
antimony  and  three  of  hydrochloric  acid  yield  one  of  the 
«esquichloride  of  antimony  and  three  of  sulphureted  hy- 
drogen. 

Sulphureted  hydrogen  is  a  colorless  and  transparent 
gas,  having  the  odor  of  rotten  eggs.     It  is  absorbed  by 

Describe  the  process  for  preparing  sulphureted  hydrogen.     What  are 
its  distinctive  properties  ? 


SULPHURETED    HYDROGEN.  221 

water  readily,  that  liquid  taking  up  two  or  three 
times  its  volume.  Its  specific  gravity  is  1-177.  It 
is  combustible,  and  may  readily,  be  burned  from  a 
jet  placed  in  the  flask  in  which  it  is  being  evolved, 
the  products  of  its  combustion  being  sulphurous 
acid  and  water  ;  but  if  the  air  in  which  it  is  burn- 
ed be  limited  in  quantity,  water  alone  is  produced 
and  sulphur  deposited.  Its  solution  in  water  decom- 
poses gradually  by  contact  with  the  air,  the  hydrogen  un- 
dergoing oxydation,  and  the  sulphur  being  set  free.  It 
has  the  properties  of  a  weak  acid,  reddening  litmus  fee- 
bly, and  yields  with  metallic  bases  water  and  sulphurets  : 

MS. 


many  of  these  sulphurets  being  insoluble  and  highly  col 
ored  :  antimony  gives  an  orange  precipitate  ;  arsenic  and 
cadmium,  yellow;  lead,  brown;  and  manganese,  flesh- 
colored.  On  this  principle,  the  presence  of  sulphureted 
hydrogen  may  be  always  detected  :  the  carbonate  of  lead, 
for  example,  is  blackened;  and  hence,  white  paint  ex- 
posed in  places  in  which  sulphureted  hydrogen  is  being 
evolved  turns  dark,  and  metallic  silver  tarnishes,  and 
finally  becomes  black.  By  a  pressure  of  about  seventeen 
atmospheres  the  gas  may  be  liquefied. 

The  action  of  sulphureted  hydrogen  on  metallic  bod- 
ies may  be  illustrated  in  a  very  interesting  manner  by 
writing  on  a  sheet  of  paper  with  a  solution  of  acetate  of 
lead,  the  letters  being  invisible  until  exposed  to  a  stream 
of  this  gas,  when  they  turn  black.  Its  action  in  producing 
precipitates  may  be  shown  by  conducting  a  stream  of  it 
through  a  solution  of  tartar  emetic,  arsenious  acid,  or 
acetate  of  lead. 

Sulphureted  hydrogen  is  sometimes  naturally  dissolved 
in  spring  water,  constituting  the  mineral  waters  of  various 
places,  as  the  Virginia  Springs.  It  is  also  said  to  be  con 
tained  in  the  brackish  water  of  the  mouths  of  large  rivers, 
due,  perhaps,  'to  the  action  of  the  organic  matter  they 
contain  upon  the  sulphates  existing  in  the  sea.  It  has 
been  thought  by  some  authors  that  the  existence  of  this 
gas  in  the  air  of  those  places  is  connected  with  the  fevers 

What  are  the  results  of  its  combustion  ?     What  is  the  nature  of  the 
precipitates  it  gives  with  metallic  oxides  ?     How  may  this  action  be  il- 
lustrated ?    Is  this  gas  soluble  in  water  ?    What  is  the  probable  cause  of 
its  occurrence  at  the  mouths  of  large  rivers  ? 
T  2 


222 


SELENIUM. PHOSPHORUS. 


which  there  prevail.     Sulphureted  hydrogen  is  exceed- 
ingly poisonous  when  respired. 

There  is  another  compound  of  sulphur  and  hydrogen, 
the  constitution  of  which  is  not  precisely  known,  though  it 
is  usually  described  as  bisulphureted  hydrogen,  and  its 
formula  is  therefore  jH~£2.  In  its  properties  it  is  said  to 
have  several  analogies  with  the  deutoxide  of  hydrogen. 

'SELENIUM.   se  =  39-6. 

This  element  was  discovered  by  Berzelius  in  certain 
varieties  of  pyrites.  It  is  a  rare  substance,  analogous,  in 
many  respects,  to  sulphur.  It  burns  in  the  air,  forming  an 
oxide  which  exhales  the  odor  of  decaying  horseradish. 

PHOSPHOEUS.    P=l5-7. 

A  remarkable  substance,  first  discovered  by  Brandt,  and 
now  extensively  procured  from  burned  bones,  in  which  it 
occurs  as  a  phosphate  of  lime.  It  is  found,  also,  in  other 
animal  products,  being  an  essential  ingredient  in  fibrin 
and  albumen,  and  also  in  the  brain  and  nervous  matter. 
Fig.  223.  To  procure  it,  burned 

bones  are  reduced  to  pow- 
der, and  digested  with  di- 
lute sulphuric  acid  ;  the  li- 
quid is  strained,  mixed  with 
powdered  charcoal,  and, 
when  dry,  introduced  into 
a  stone-ware  retort,  #,  Fig. 
223,  to  the  neck  of  which 
a  bent  copper  tube,  b,  is  at- 
tached, the  mouth  of  which 
dips  beneath  water.  The 
retort  being  now  exposed 
in  a  furnace  to  a  white  heat, 
half  the  phosphoric  acid  in 
the  mixture  is  deoxydized 
by  the  charcoal,  carbonic  oxide  gas  escaping,  and  phospho- 
rus distilling  over. 

Phosphorus  is  commonly  transparent  and  colorless. 
When  exposed  to  the  light  it  turns  of  a  deep  red,  and  this 
takes  place  in  a  vacuum,  or  in  gases  which  have  no  action 
on  the  phosphorus.  In  lustre  and  general  appearance  it 

What  other  compound  of  sulphur  and  hydrogen  is  there  ?  What  is  se- 
lenium ?  From  what  source  is  phosphorus  derived  ? 


PROPERTIES    OF    PHOSPHORUS.  223 

has  a  waxy  aspect.  Exposed  to  the  air  it  smokes,  and  in 
a  dark  place  shines — a  property  from  which  its  name  is 
derived.  During  this  slow  oxydation  it  exhales  an  odor 
much  resembling  that  experienced  when  an  electrical  ma- 
chine is  in  high  activity.  At  32°  it  is  brittle,  at  113°  it 
melts,  at  572°  it  boils,  distilling  over  unchanged,  if  oxy- 
gen be  absent.  But  in  the  air  it  takes  fire  and  burns  at 
about  120°,  with  evolution  of  flakes  of  anhydrous  phos- 
phoric acid.  Its  specific  gravity  is  1*77. 

From  the  intense  affinity  which  phospl'orus  has  for  oxy- 
gen, it  requires  to  be  kept  under  the  surface  of  water. 
It  is  met  with  in  commerce  in  the  form  of  small  sticks,  a 
form  given  to  it  by  melting  it  in  glass  tubes  under  warm 
water,  and  pushing  the  resulting  cylinders  out  as  soon  as 
they  have  set.  If  kept  in  an  opaque  bottle  it  is  white,  but 
it  slowly  turns  more  or  less  red  on  exposure  to  the  day- 
light. 

From  the  facility  with  which  it  takes  fire,  it  is  necessary 
to  handle  it  very  carefully,  and  to  avoid  keeping  it  in  con- 
tact with  the  warm  hand  too  long.  A  few  particles  of 
dry  phosphorus  placed  between  two  pieces  of  brown  pa- 
per and  rubbed  with  a  hard  body,  take  fire  and  burn  fu- 
riously as  soon  as  the  papers  are  separated.  It  is  upon 
this  principle  that  it  will  readily  inflame  by  the  heat  of 
friction,  that  its  useful  application  in  the  manufacture  of 
friction  matches  depends.  In  chlorine,  or  the  vapor  of 
bromine  and  iodine,  it  takes  fire  spontaneously. 

There  are  several  compounds  of  phosphorus  and  oxy- 
gen, as  follows : 

PSO  .  .  P2O  . .  P2O3 . .  P3O5. 
These  are  respectively 

Oxide  of  phosphorus.  Phosphorous  acid. 

Hypophosphorous  acid.  Phosphoric  acid. 

What  remarkable  property  does  this  body  possess  ?  Why  is  phosphorus 
to  be  kept  under  the  surface  of  water  ?  What  is  the  action  of  light  upon 
it  1  What  useful  application  is  made  of  its  ready  combustibility  ?  How 
many  compound  of  phosphorus  and  oxygen  are  were  ? 


224  PHOSPHORUS  AND  OXYGEN. 


LECTURE  L. 

COMPOUNDS  OF  PHOSPHORUS  AND  OXYGEN. — Oxide  of 
Phosphorus. — Preparation  of. — Hypophosphorous  and 
Phosphorous  Acids. — Phosphoric  Acid. —  Three  States 
of  Hydra ( -ion. — Properties  of  these  three  Acids. —  Their 
Salts. — Phosphureted  Hydrogen.  —  Spontaneously  In- 
flammable and  Non-inflammable  Varieties. — CHLORINE. 
— Preparation  of. — Its  Relations  to  Combustion  and 
Respiration. 

OXIDE  OF  PHOSPHORUS.    P3O  =  55-113. 
Fig.  224.  THIS  oxide  may  be  formed  by  causing 

a  stream  of  oxygerf  gas,  from  the  tube  a, 
Fig.  224,  to  be  directed  upon  phospho- 
rus under  hot  water  in  a  glass,  I.  A 
brilliant  combustion  under  the  water  is 
the  result,  with  the  production  of  phos- 
phoric acid  and  of  a  red  powder,  which 
is  the  substance  in  question. 

HYPOPHOSPHOROUS  ACID,  P2O= 39-413, 
is  very  little  known ;   it  is  formed  when  phosphorus  is 
boiled  in  alkaline  solutions. 

PHOSPHOROUS  ACID,  P2Oa  =  55-439, 

is  formed  during  the  slow  combustion  of  phosphorus  in  the 
air ;  it  may  also  be  produced  by  acting  on  the  sesquichlo- 
ride  of  phosphorus  with  water.  The  solution  of  this  acid 
is  sometimes  used  as  a  deoxydizing  agent. 

PHOSPHORIC  ACID.     P2O5  =  71-465. 

Anhydrous  phosphoric  acid  is  formed 
when  phosphorus  burns  in  dry  air  or  ox- 
ygen gas  (Fig.  225).  It  condenses  m 
white  flakes  of  a  snowy  appearance,  and 
possesses  an  intense  affinity  for  water,  in 
which,  if  placed,  it  hisses  like  a  red-hot 
iron.  It  can  scarcely  be  said  to  possess 
acid  properties.  Until  it  has  united  with 
water,  those  properties  are  very  feebly  developed. 

How  is  oxide  of  phosphorus  made  ?  What  is  its  appearance  ?  How 
are  hypophosphorous  and  phosphorous  acids  produced  1  Under  what  *ur- 
cumstances  is  anhydrous  phosphoric  acid  produced  7 


ACIDS    OF    PHOSPHORUS.  225 

With  water,  phosphoric   acid  unites  in  three  propor 
tions,  producing 

Monobasic  phosphoric  acid    .     .    P2O5  +    HO,  or    H  -f-  P2O$. 
Bihasic  "  .    .    PaOs-f-  2//O,  or  2#-f-  PiO7 

Tribasic  "  .     .    P3O5  +  3#U  or  3^-f-  P*Od. 

These  acids  also  have  the  names  of  metaphosphoric,  pyro 
phosphoric,  and  common  phosphoric  acids  respectively 
Either  of  them  may  exist  in  solution  with  water. 

Metaphosphoric,  or  the  monobasic  phosphoric  acid,  may 
be  obtained  by  dissolving  phosphorus  in  dilute  nitric 
acid,  evaporating,  and  exposing  the  residue  to  a  red  heat. 
It  may  also  be  obtained  by  dissolving  the  anhydrous  acid 
in  water,  evaporating  and  igniting  it.  In  both  these  cases 
a  transparent  body,  like  ice  or  glass,  is  produced  ;  hence 
called  glacial  phosphoric  acid.  It  contains  one  atom  of 
water,  which  can  not  be  removed  from  it  by  heat. 

Monobasic  phosphoric  acid  is  characterized  by  giving 
a  white  granular  precipitate  with  nitrate  of  silver ;  it  also 
coagulates  albumen,  producing  white  curds.  If  kept  in 
a  solution  of  water,  or  boiled  with  it,  it  passes  into  the 
tribasic  state. 

Pyrophosphoric,  or  bibasic  phosphoric  acid,  may  be 
obtained  by  heating  the  common  phosphoric  acid  to 
417°  F.  for  some  time.  In  solution  it  neither  precipi- 
tates silver  nor  coagulates  albumen,  but  its  salts  yield, 
with  silver,  a  flaky  white  precipitate.  Like  the  former, 
this  turns  into  the  tribasic  acid  by  boiling  with  water. 

Common,  or  the  tribasic  phosphoric  acid,  may  be  ob- 
tained from  bone  earth  by  the  action  of  oil  of  vitriol, 
which  yields  a  precipitate  of  sulphate  of  lime  ;  or,  more 
easily,  by  boiling  a  solution  of  the  anhydrous  phosphoric 
acid.  In  solution  it  neither  precipitates  silver  nor  coagu- 
lates albumen,  but  its  salts  yield  a  Canary-yellow  precip- 
itate with  the  nitrate  of  silver.  By  exposure  to  a  low 
heat  it  becomes  bibasic,  and  to  a  red  heat,  monobasic. 

These  hydrogen  acids  of  phosphorus  give  rise  to  a 
very  extensive  and  complex  class  of  salts,  according  to 
the  extent  to  which  their  hydrogen  is  replaced  by  metal- 
lic bodies.  Thus,  the  monobasic  phosphoric  acid  can 
yield  only  one  series  of  salts,  in  which  all  its  hydrogen  is 

How  many  compounds  does  it  yield  with  water  ?  How  is  metaphos- 
phoric acid  made  ?  What  is  glacial  phosphoric  acid  ?  What  are  the 
properties  characteristic  of  monobasic,  bibasic,  and  tribasic  phosphoric 
acids  respectively  ?  How  many  series  of  salts  can  each  yield  1 


226 


PHOSPHURETED    HYDROGEN. 


replaced  by  a  metal;  but  the  bibasic  can  yield  two  differ- 
ent series,  according  as  the  metal  replaces  one  or  both 
atoms  of  base  ;  and  the  tribasic  can  yield  three  different 
series,  according  as  one  or  two  or  all  three  of  its  hydro- 
gen atoms  are  replaced. 

PHOSPHURETED  HYDROGEN,  PiHa  =  34-4, 
may  be  made  by  boiling  phosphorus  in  a  strong  solution 
of  lime  or  potash  in  a  retort,  a,  Fig.  226,  the  neck  of 


Fig.  226. 


which  dips  beneath  the  surface  of  water,  a  few  drops  of 
ether  being  previously  put  into  the  retort.  As  the  bub- 
bles of  gas  break  on  the  water,  they  take  fire,  burning 
with  a  bright  yellow  light,  and  there  ascends  through  the 
air  a  ring  of  gray  smoke,  which  dilates  as  it  rises,  and 
exhibits  a  curious  rotatory  movement  of  its  parts.  This 
gas,  also,  may  be  made  by  bringing  the  phosphuret  of  cal- 
cium in  contact  with  water. 

Phosphureted  hydrogen  is  a  colorless  gas,  exhaling  a 
peculiar  odor,  like  garlic,  and,  when  burning,  produces 
phosphoric  acid  and  water.  It  exists  under  two  forms : 
1st.  Spontaneously  inflammable;  2d.  Not  spontaneously 
inflammable.  It  is  said  that  the  first  may  be  changed  into 
the  second  by  small  quantities  of  the  vapor  of  ether,  oil  of 
turpentine,  &c.,  and  the  second  into  the  first  by  the  addi- 
tion of  a  minute  quantity  of  nitrous  acid. 

CHLORINE.     Cl^=  35-47. 

Chlorine  is  found  abundantly  in  nature  in  union  with  so- 
dium, forming  common  salt,  a  substance  which,  for  the 
most  part,  gives  to  the  sea  water  its  salinity,  and  consti- 

Describe  the  preparation  of  phosphureted  hydrogen.  What  are  the 
properties  of  phosphureted  hydrogen  ?  How  may  its  two  forms  be  con- 
verted into  each  other  1  In  what  substances  does  chlorine  chiefly  occur  ? 


PREPARATION    OF    CHLORINE. 


227 


tutes  the  deposits  of  rock  salt.     It  is,  therefore,  an  abund- 
ant substance. 

Chlorine  is  best  made  by  the  action  of  hydrochloric  acid 
on  peroxide  of  manganese  : 

MnO,  +  2HCI...  =  ...MnCl  +  2HO  +  Cl; 
that  is,  one  atom  of  peroxide  of  manganese  and  two  of 
hydrochloric  acid  yield  one  atom  of  the  chloride  of  man- 
ganese, two  of  water,  and  one  of  chlorine.  Half  the  chlo- 
rine is,  therefore,  given  off  as  chlorine  gas,  and  the  other 
half  remains  as  chloride  of  manganese. 

Chlorine  gas  being  very  soluble  in  cold  water,  and  act- 
ing with  great  energy  on  mercury,  it  can        Fig.  227. 
neither  be  collected  at  the  water  nor  mercu- 
rial trough  ;  but,  having  a  specific  gravity  of 
2-470,  we  are  able  to  collect  it  by  the  meth- 
od of  displacement,  as  shown  in  Fig.  227. 
It  may,  however,  also  be  collected  over  warm 
water  or  a  saturated  solution  of  common  salt. 

When  chlorine  is  required  in  a  state  of  dryness,  it  may 
be  obtained  by  an  apparatus  like  that  represented  in  Fig. 
a  is  the  retort  containing  the  hydrochloric  acid  and 


228. 


Fig.  22a 


manganese.  It  is  connected  with  a  small  receiver,  t>, 
which  retains  part  of  the  water  which  the  gas  may  bring 
over ;  this,  again,  is  connected  with  a  chloride  of  calcium 
tube,  c,  which  effects  the  perfect  drying  of  the  gas. 

Chlorine  is  a  gas  of  a  pale,  yellowish  green  color.  It  may 

How  may  it  be  formed?    What  are  its  properties?    How  is  it  pro- 
cured in  a  state  of  dryness  ? 


228  PROPERTIES    OF    CHLQIUXE. 

be  liquefied  by  a  pressure  of  four  atmospheres.  A  taper 
immersed  in  it  burns  for  a  few  minutes  with  a  dull  red 
flame,  emitting  volumes  of  smoke,  due  to  the  fact  that  the 
Fig.  229.  hydrogen  of  the  flame  continues  to  burn  or  unite 
with  the  chlorine,  forming  hydrochloric  acid ;  but 
the  carbon,  having  little  affinity  for  chlorine,  is 
set  free  in  an  uncombined  state,  as  lampblack. 
Powdered  antimony,  or  thin  brass  leaf,  plunged 
in  this  gas,  becomes  incandescent,  and  burns,  pro- 
ducing a  chloride.  A  piece  of  phosphorus  im- 
mersed in  it  takes  fire  at  common  temperatures, 
and  burns  with  a  pale  flame.  The  smell  of  chlo- 
rine is  disagreeable,  and  its  effect,  even  in  a  diluted  state, 
suffocating.  It  irritates  the  air  passages  of  the  lungs, 
producing  hiccough  and  an  unpleasant  expectoration 


LECTURE  LI. 

CHLORINE,  CONTINUED. — Bleaching  Properties. —  Combus- 
tion of  Hydrocarbons. — Disinfecting  Qualities. — Com- 
pounds with  Oxygen.  —  Properties  of  Hypochlorous, 
Chlorous,  and  Chloric  Acids. — Quadrochloride  of  Nitro- 
gen.— Hydrochloric  Acid. — Preparation  in  the  Gaseous 
and  Liquid  States. 

THE  most  valuable  property  of  chlorine  is  its  power  of 
discharging  vegetable  colors,  on  which  is  founded  its  ap- 
plication in  the  arts  of  bleaching  arid  calico  printing.  This 
Fig.  230.  property  may  be  illustrated  in  many  ways.  By 
pouring  a  solution  of  litmus  or  indigo  through  a 
funnel,  a,  Fig.  230,  into  a  flask,  b,  containing  chlo- 
rine gas,  the  decoloration  takes  place  instantly,  or, 
,  "b  if  the  color  is  not  completely  discharged,  it  will  be 
found,  in  a  short  time,  to  disappear.  The  same 
takes  place  when  a  solution  of  chlorine  in  water  is 
used. 

The  peculiarities  of  chlorine  in  supporting  combustion 
are  remarkable,  when  compared  with  those  of  oxygen 

What  are  its  relations  in  the  combustion  of  a  taper,  and  how  does  it  act 
on  certain  metals  and  phosphorus?  What  is  its  effect  on  the  animal 
system  ?  Of  the  properties  of  chlorine,  which  is  the  most  valuable  ?  How 
may  it  be  illustrated  ? 


PROPERTIES  OF  CHLORINE.  229 

gas.     A  piece  of  paper,  Fig.  231,  dipped  in  oil   Figm  231 
of  turpentine,  takes  fire  in  a  moment  at  com- 
mon temperatures,  when  placed  in  a  jar  of  chlo- 
rin-e,  arid,  as  we  have  seen,  phosphorus  and  sev- 
eral of  the  metals  undergo  spontaneous  ignition 
in  the  same  manner.     These  phenomena  depend 
on  the  intense  affinity  which  chlorine  has  for  elec- 
tro-positive bodies,  but  it  is  very  remarkable  that 
it  seems  to  have  little  disposition  to  unite  with 
carbon.     As  in  the  burning  of  a  taper,  so  in  this  exper- 
iment with  turpentine,  it  is  the  hydrogen  which  burns,  and 
the  carbon  is  evolved  in  clouds  of  smoke. 

Chlorine  is  also  used  by  physicians  for  the  purpose  of 
destroying  miasmata,  and  the  effluvia  of  sickrooms  or  oth- 
er places.  It  is  necessary,  from  its  irrespirable  qualities, 
to  disengage  it  slowly  and  with  caution  where  patients 
are  present.  The  chlorides  of  soda  and  lime  are  common- 
ly used. 

Free  chlorine  may  be  detected  by  its  smell,  its  bleach- 
ing action  on  indigo  solution,  and  giving  a  white,  curdy 
precipitate  with  the  nitrate  of  silver.  Its  solution  in  water 
is  readily  made  by  introducing  a  small  quantity  of  water 
into  a  bottle  full  of  chlorine,  agitating  it,  and  Opening  the 
mouth  of  the  bottle  from  time  to  time  under  water ;  the 
gas  being  gradually  absorbed,  the  bottle  becomes  full  of 
water,  which,  of  course,  contains  its  own  volume  of  chlo- 
rine. This  solution  decomposes  in  the  sunshine,  evolving 
oxygen  gas,  the  water  being  decomposed.  With  oxygen 
chlorine  unites  in  several  proportions,  producing, 

CIO  .  .  CIO. .  .  CIO, .  .  CIO,. 
They  are  designated 

Hypochlorous  acid.  Chloric  acid 

Chlorous  acid.  Perchloric  acid. 

HYPOCHLOROUS  ACID.     CIO  =  43-483. 

Hypochlorous  acid  may  be  obtained,  by  agitating  the 

red  oxide  of  mercury,  suspended  in  water,  with  chlorine. 

If  a  strong  solution  of  it  be  placed  in  an  inverted  tube, 

and  pieces  of  dry  nitrate  of  lime  be  added,  the  gas  is  dis- 

What  is  the  cause  of  the  clouds  of  smoke  deposited  when  carburets  of 
hydrogen  burn  in  chlorine  gas  ?  For  what  purpose  is  chlorine  used  by 
physicians  ?  How  may  chlorine  be  detected  ?  How  may  a  solution  of  it 
be  made?  What  compounds  of  chlorine  and  oxygen  are  known  ?  How 
is  hypochlorous  acid  made,  and  what  are  its  properties  ? 


230  ACIDS    OF    CHLORINE. 

engaged,  and  rises  to  the  top  of  the  tube.  It  is  of  a  deep- 
er color  than  chlorine,  bleaches  powerfully,  and,  by  a 
slight  elevation  of  temperature,  explodes,  evolving  two 
volumes  of  chlorine  and  one  of  oxygen  gas. 

The  bleaching  compounds  are  compounds  of  chlorides 
and  hypochlorides.  They  are  easily  decomposed  by 
acids.  Thus,  when  chloride  of  lime  is  to  be  used  for  dis- 
infecting purposes,  it  ie  merely  required  to  expose  it  with 
water  to  the  carbonic  acid  of  the  air,  or  to  add  a  little  of 
it,  from  time  to  time,  to  a  vessel  containing  dilute  sulphur- 
ic acid. 

CHLOROUS  ACID,  CIO4  =  67-522, 

may  be  made  by  cautiously  acting  on  small  quantities  of 
chlorate  of  potash  with  sulphuric  acid.  It  is  a  yellow 
gas,  which  explodes  furiously  from  very  slight  causes,  the 
warmth  of  the  hand  being  often  sufficient  to  give  rise 
to  a  violent  action.  It  contains  two  volumes  of  chlorine 
and  four  of  oxygen,  condensed  into  four  volumes.  It  may 
be  conveniently  made  by  operating  on  a  few  grains  of  the 
Fig  232  chlorate  in  a  test  tube.  If  into  a  glass,  a,  Fig. 
232,  containing  water,  a  small  quantity  of  chlo- 
rate of  potash  is  placed,  and  upon  it  a  few  frag- 
ments of  phosphorus,  and  sulphuric  acid  be 
poured  through  a  funnel,  b,  so  as  to  act  on  the 
chlorate,  chlorous  acid  is  set  free  ;  it  communi- 
cates a  golden  yellow  color  to  the  water,  and 
as  each  bubble  passes  by  the  phosphorus  it  sets  it  on  fire, 
furnishing  a  beautiful  instance  of  combustion  under  water. 

CHLORIC  ACID,  CIO*  =  75-535, 

may  be  made  by  decomposing  the  chlorate  of  baryta  by 
sulphuric  acid,  and  evaporating  the  solution.  It  is  a  yel- 
low, viscid  acid :  a  piece  of  paper  dipped  in  it  is  set  on 
fire.  It  does  not  bleach.  It  forms  salts,  one  of  which,  the 
chlorate  of  potash,  is  of  considerable  importance,  and  is 
used  for  the  preparation  of  oxygen.  A  few  grains  of  the 
chlorate  of  potash,  ground  in  a  mortar  with  a  pinch  of 
flowers  of  sulphur,  explodes  incessantly  during  the  tritu- 
ration. 

PERCHLORIC  ACID.     ClOt  =  91-561. 
The  perch  (.orate  of  potash  forms  along  with  the  chloride 

What  are  the  properties  of  chloric  acid?     How  may  the  combustion  of 
phosphorus  under  water  be  produced  by  it  ?    How  is  chloric  acid  made  ? 


HYDROCHLORIC    ACID.  231 

of  potassium  when  one  third  of  its  oxygen  is  expelled 
from  chlorate  of  potash ;  the  two  salts  may  be  separated 
from  each  other  by  boiling  in  water,  the  perchlorate  crys- 
tallizing on  cooling.  From  this  perchloric  acid  may  be 
obtained  by  distillation  with  an  equal  weight  of  oil  of  vit- 
riol, mixed  with  half  as  much  water.  It  may  be  obtained 
in  the  form  of  a  white  crystalline  mass,  very  deliquescent, 
and  its  solution  is  sometimes  used  as  a  test  for  potash, 
with  which  it  gives  a  sparingly  soluble  salt.  The  solu- 
tion fumes  in  the  air,  has  a  specific  gravity  of  1*65,  and 
does  not  posse-ss  bleaching  properties. 

CHLORINE  AND  NITROGEN. 

These  substances  unite,  forming  an  oily  liquid,  when  a 
warm  solution  of  sal  ammoniac  is  exposed  to  chlorine  gas. 
The  resulting  body  is  regarded  as  a  quadrichloride  of 
nitrogen  (NC14).  By  its  violent  explosions,  several  emi- 
nent chemists  have  been  seriously  injured.  The  mere 
contact  of  oily  matter  produces  a  detonation. 

CHLORINE  AND  ^HYDROGEN. 

HYDROCHLORIC   ACID.     HCl  =  36-47. 

This  acid,  called  also  muriatic  acid,  is  easily  prepared 
by  placing  in  a  flask  six  parts  of  common  salt  and  ten 
parts  by  weight  of  oil  of  vitriol,  mixed  with  four  of  water, 
the  mixture  being  suffered  to  cool  before  it  is  introduced. 
On  heating  the  mixture,  hydrochloric  acid  is  evolved, 
which  passes  along  a  bent  tube  into  a  bottle  containing 
six  parts  (by  weight)  of  water.  The  end  of  the  tube  dips 
but  a  very  short  distance  beneath  the  surface  of  this  wa- 
ter, so  that  if  the  liquid  should  rise  it  may  be  received 
into  a  ball  blown  upon  the  tube,  and  the  extremity  of  the 
tube  becoming  uncovered,  atmospheric  air  may  pass  into 
the  interior  of  the  flask.  At  the  close  of  the  process,  the 
liquid  in  the  bottle,  which  should  be  constantly  surrounded 
by  ice  water  in  a  small  tank,  more  than  doubles  its  volume, 
and  is  a  pure  solution  of  hydrochloric  acid.  The  action  is 
NaCl  +  2(HO,  S03).  ..  =  ... HCl  +  (NaO,HO,2SO3); 
that  is,  one  atom  of  chloride  of  sodium  and  two  of  sul- 
phuric acid  yield  one  atom  of  hydrochloric  acid  and  one 
of  the  bisulphate  of  soda. 

How  is  perchloric  acid  prepared,  and  for  what  purpose  is  it  used? 
What  are  the  properties  of  the  chloride  of  nitrogen  ?  How  is  hydrochloric 
acid  made  ? 


232  IIYDROCHLOIIIC    ACID. 

From  the  liquid  thus  produced,  or  from  the  commercial 
muriatic  acid,  by  heating  in  a  flask,  pure  hydrochloric 
acid  gas  may  be  obtained ;  it  may  also  be  less  advanta- 
geously procured  by  the  direct  action  of  strong  oil  of  vit- 
riol on  common  salt,  the  reaction  in  this  case  being 
NaCl  +  HO,  SO3...  =  ... HCl  +  NaO,  SO,. 

Pure  hydrochloric  acid  is  a  transparent,  colorless  gas, 
possessing  powerful  acid  qualities,  very  absorbable  by  wa- 
ter, which  liquid  takes  up  several  hundred  times  its  own. 
volume  of  the  gas  ;  it  fumes  in  moist  air,  and  has  a  pungent 
odor.  If  a  dry  Florence  flask  (Fig.  233)  be 
filled  with  it  by  the  process  of  displacement, 
and  the  mouth  of  it  opened  under  the  surface 
of  cold  water,  the  water  rushes  up  into  the 
flask,  absorbing  the  gas  with  great  violence. 
The  specific  gravity  of  hydrochloric  acid  is 
1'284.  It  contains  equal  volumes  of  its  constituents,  uni- 
ted without  condensation. 


LECTURE  LII. 

CHLORINE,  CONTINUED. — Production  of  Hydrochloric  Acid 
by  Light. — Action  of  Hydrochloric  Acid  on  Metallic 
Protoxides. — Muriatic  Acid  Solution. — Detection  of  Hy- 
drochloric Acid. — Nitromuriatic  Acid. — IODINE. — Sour- 
ces of. — Preparations  and  Properties. —  Tests  for  Iodine. 
—  Its  Action  on  Starch. — Hydriodic  Acid. —  Oxygen 
Compounds  of  Iodine. 

PURE  hydrochloric  acid  gas  is  also  obtained  when  a 
mixture  of  chlorine  and  hydrogen,  in  equal  proportions, 
is  exposed  to  the  light.  In  the  dark  these  gases  appear 
to  have  no  disposition  to  unite,  but  if  they  be  placed  in  a 
flask  covered  over  with  a  wire  screen,  and  a  beam  of  the 
sunlight  reflected  upon  them  from  a  looking-glass,  a  vio- 
lent explosion  ensues  and  hydrochloric  acid  is  formed. 

I  have  found  that,  in  this  remarkable  experiment,  the 
action  is  chiefly  due  to  the  chlorine,  which,  from  being  in 

How  may  the  gas  be  procured  ?  What  are  the  properties  of  hydro- 
chloric acid  gas  ?  How  may  its  affinity  for  water  be  proved  ?  What  is 
its  constitution  ?  What  is  the  action  of  sunlight  on  a  mixture  of  chlorine 
and  hydrogen  ?  To  which  of  these  bodies  is  this  action  due  ? 


PROPERTIES    OF    HYDROCHLORIC    ACID.  233 

a  passive,  assumes  an  active  state  by  exposure  to  rays  of 
an  indigo  color.  It  may  be  thrown  into  the  same  condi- 
tion in  many  other  ways  ;  for  example,  by  the  contact  of 
spongy  platina.  Moreover,  when  chlorine  by  itself  has 
been  exposed  to  the  sun,  it  gains  the  quality  of  uniting 
more  easily  with  hydrogen  than  chlorine  which  has  been 
made  and  kept  in  the  dark. 

When  hydrochloric  acid  is  brought  in  contact  with 
metallic  oxides,  decomposition  of  both  ensues,  and  metallic 
chlorides  are  formed,  thus  : 

MO     +      HCl  ...  =  ...  MCI    +    HO. 
or,       M.203  +  3(HCI)...  =  ...M,C13+3HO; 
that  is,  one  atom  of  a  metallic  protoxide  with  one  atom 
of  hydrochloric  acid  yields  one  atom  of  a  protochloride  of 
the  metal  and  one  of  water.     But,  in  the  case  of  a  sesqui- 
oxide,  one  atom  of  it  with  three   of  hydrochloric   acid 
yield  one  atom  of  the  metallic  sesquichloride  and  three  of 
water. 

The  constitution  of  hydrochloric  acid,  and  its  Fig.  234. 
action  on  metallic  oxides,  may  be  strikingly  illus- 
trated by  taking  a  flask,  b  (Fig.  234),  filled  with 
it,  in  a  perfectly  dry  state,  and  allowing  the  perox- 
ide of  mercury,  in  fine  powder,  to  fall  through  it. 
The  bichloride  of  mercury,  corrosive  sublimate, 
instantly  forms,  and  drops  of  water  make  their  ap- 
pearance on  the  sides  of  the  flask. 

It  is  under  the  form  of  a  solution  in  water,  as  liquid 
muriatic  acid,  or  spirit  of  salt,  that  hydrochloric  acid  is 
chiefly  used.  The  mode  of  obtaining  it  has  been  described 
in  the  last  Lecture.  This  liquid,  when  concentrated,  has 
a  specific  gravity  of  1*21,  and  contains  42  percent,  of  acid. 
It  smokes  in  the  air,  and  reddens  blue  litmus  powerfully. 
The  commercial  acid  is  usually  of  a  yellow  color ;  it  con- 
tains chloride  of  iron,  derived  from  the  iron  vessels  from 
which  it  is  distilled.  It  also  often  contains  sulphuric  acid, 
chlorine,  sulphurous  acid,  tin,  or  arsenic,  and  is,  therefore, 
best  prepared  by  the  process  described,  which  yields  it  in 
perfect  purity. 

Hydrochloric  acid  may  be  detected  by  yielding,  when 

What  is  the  action  of  hydrochloric  acid  on  metallic  oxides  ?  What  are 
the  products  of  the  action  of  hydrochloric  acid  on  peroxide  of  mercury  ? 
What  are  the  properties  of  liquid  muriatic  acid  ?  What  are  its  ioa 
purities  ? 

U2 


234  NITROMURIATIC    ACID. 

in  a  free  state  with  ammonia,  dense  white  clouds 
of  sal  ammoniac.  If  two  glasses,  one  filled 
with  this  acid,  and  the  other  with  ammonia,  be 
brought  near  each  other,  a  white  cloud  forms  be- 
tween them.  A  glass  rod,  a  (Fig.  236),  dipped 
in  ammonia  may  be  used  for  the  same  Fig  236> 
purpose.  With  nitrate  of  silver  hydrochloric  /g&fc 
acid  yields  a  white  chloride  of  silver,  which  SaPg, 
turns  black  in  the  light,  being  the  same  pre- 
cipitate given  under  the  same  circumstances 
by  free  chlorine.  From  this  latter  substance 
it  maybe  distinguished  by  litmus  water,  which 
is  bleached  by  chlorine,  and  reddened  by  hydrochloric  acid. 
Nitromuriatic  acid,  or  aqua  regia,  is  formed  by  adding 
to  hydrochloric  acid  one  half  or  a  third  of  its  volume  of 
nitric  acid.  The  nitric  acid,  furnishing  oxygen  to  the  hy- 
drochloric acid,  forms  water,  and  chlorine,  with  nitrous 
acid,  is  set  free  in  the  solution.  Aqua  regia  is  used  as  a 
solvent  for  platina  and  gold,  a  result  which  may  be  illus- 
trated by  placing  a  sheet  of  gold  leaf  in  the  mixture. 

IODINE.     7=126-57. 

Iodine  chiefly  occurs  in  the  products  of  the  sea,  being 
found  in  sea-weed,  sponge,  &c. ;  also  in  certain  brine 
springs,  and  in  some  ores  of  silver  and  zinc. 

It  may  be  obtained  by  lixiviating  the  ashes  of  sea- weeds, 
and  evaporating  the  solution  until  no  more  crystals  are  de- 
posited. The  residual  liquor  is  then  acted  upon  by  sul- 
phuric acid,  and  subsequently  heated  with  peroxide  of 
manganese,  in  a  leaden  retort,  a  b  c  (Fig.  237,  page  235), 
the  iodine  distills  over  into  the  receivers,  d. 

It  is  a  solid  substance,  of  a  deep  blue  or  black  appear- 
ance, with  a  semi-metallic  lustre,  communicates  to  the 
skin  a  fugitive  yellow  stain,  and  exhales  an  odor  like  that 
of  sea  beaches.  It  crystallizes  in  rhomboidal  plates,  is 
brittle,  and  has  a  specific  gravity  of  4*948.  At  225°  it  melts, 
and  boils  at  347°,  exhaling,  even  at  moderate  tempera- 
tures, a  splendid  purple  vapor,  from  which  its  name  is  de- 
rived. The  specific  gravity  of  this  vapor  is  8*707 ;  it  is, 
therefore,  one  of  the  heaviest  gaseous  bodies  known. 

How  may  hydrochloric  acid  be  detected?  "What  is  the  preparation 
and  property  of  nitromuriatic  acid  ?  From  what  source  is  iodine  procured  ? 
What  is  the  method  of  its  preparation  ?  What  is  its  appearance  ?  "What 
is  the  color  of  its  vapor  ?  From  what  circumstance  is  its  name  derived? 


235 


Iodine   supports   combustion   much  in  the      Fig.  238. 
same  manner  as  chlorine.     A  jar,  a  (Fig.  238), 
containing  a  few  grains  of  it,  placed  in  a  small 
sand  bath,  b,  and  warmed  by  a  spirit  lamp,  c, 
may  be  easily  filled  with  its  dense  vapor,  the 
atmospheric  air  floating  out  before  it.     In  this 
vapor  if  a  lighted  taper  is  plunged,  it  exhibits 
a  retarded  combustion ;  but  a  piece  of  phos- 
phorus, introduced  on  a  spoon,  takes  fire  and  burns.     In 
the  same  manner,  if  a  quantity  of  iodine          Fig,  23g 
be  placed  in  a  small  capsule,  and  upon  it 
a  fragment  of  dry  phosphorus  (Fig.  239), 
spontaneous  ignition  ensues,  with  the  ev- 
olution of  phosphoric  acid,  and  the  vapor 
of  iodine,  iodide  of  phosphorus  remaining 
in  the  capsule. 

In  water,  iodine  is  but  slightly  soluble, 
that  liquid  taking  up  r^Vf™  Part  of  its 
weight  and  assuming  a  brown  color.  Alcohol  dissolves 
it  freely,  forming  tincture  of  iodine.  In  solutions  of  the 
iodides  iodine  may  be  dissolved. 

With  many  substances  iodine  gives  characteristic  reac- 
tions.    The  iodide  of  potassium,  with  the  acetate  of  lead, 

What  are  its  relations  as  respects  combustion  ?    Is  it  soluble  in  water 
and  alcohol? 


236  HYDRIODIC    ACID. 

yields  a  golden  yellow  precipitate  ;  with  the  bichloride  of 
mercury,  a  fine  scarlet-colored  biniodide.  This  substance 
possesses  the  singular  quality  that,  if  dried  and  sublimed 
in  a  tube,  it  yields  crystals  of  a  brilliant  yellow  aspect, 
which  become  red  on  being  simply  touched  with  a  hard 
body.  With  a  solution  of  starch  free  iodine  yields  a  deep 
blue  color,  the  solution  becoming  colorless  if  heated,  but 
the  blue  color  returning  on  cooling,  provided  the  temper- 
ature has  not  been  carried  to  the  boiling  point.  If  a  po- 
tato be  cut  in  two,  and  a  little  tincture  of  iodine  poured 
on  the  surface,  innumerable  blue  specks  make  their  ap- 
pearance, each  corresponding  to  the  position  of  a  granule 
of  starch.  Starch  and  free  iodine  will,  therefore,  mutually 
detect  the  presence  of  each  other. 

HYDRIODIC  ACID.    HI=  127-57 

Hydriodic  acid  gas  may  be  obtained  by  dissolving  in  a 
solution  of  iodide  of  potassium  as  much  iodine  as  it  will 
hold,  adding  small  pieces  of  phosphorus,  and  warming  the 
mixture.  A  colorless  transparent  gas  is  evolved,  which 
fumes  in  the  air,  and  may  be  collected  over  mercury.  Its 
specific  gravity  is  4*384.  It  has  the  general  relations  of 
hydrochloric  acid,  and,  like  it,  is  very  soluble  in  water. 
Fig.  240.  A  solution  of  hydriodic  acid  in  water  may 

be  made  by  passing  a  stream  of  sulphureted 
hydrogen  from  a  flask,  a  (Fig.  240),  through 
L   water,  b,  in  which  that  substance  is  suspend- 
ed.   The  acid  forms  and  sulphur  is  deposited  : 

I+HS...  =  ...S  +  HI. 
With  nitrate  of  silver  this  acid  yields  a  pale  yellow  pre- 
cipitate, the  iodide  of  silver.  This  is  the  substance  which 
forms  the  basis  of  the  remarkable  compound  used  in  the 
Daguerreotype.  In  that  case  it  is  formed  by  holding  a 
plate  of  pure,  polished  silver  in  the  vapor  of  iodine  ;  the 
plate  tarnishes  and  turns  yellow,  and,  if  set  in  the  sun- 
shine, turns  promptly  of  a  deep  olive  black. 

Iodine  yields  two  oxygen  acids,  iodic  (1O5)  and  peri- 
odic acid  (IO7).  With  nitrogen,  also,  it  gives  NI4,  char- 
acterized, like  the  analogous  compound  of  chlorine,  by  the 
facility  with  which  it  explodes. 

How  may  it  be  detected?  In  what  manner  is  hydriodic  acid  made? 
What  is  the  simplest  method  of  obtaining  a  solution  of  it  ?  "What  is  the 
precipitate  it  yields  with  nitrate  of  silver  ?  What  are  the  oxygen  com« 
pounds  of  iodine  ? 


BROMINE.  287 


LECTURE  LIII. 

BROMINE — FLUORINE. — Bromine. — Sources  of. — Proper- 
ties . — Compounds  of. — FLUORINE. — Hydrofluoric  Acid. 
— Its  Properties  and  Action  on  Glass. — CARBON. — Allo- 
tropic  Forms  of. — Preparation  of  some  of  those  Forms. 
— Diamond. — Oxygen  Compounds  of  Carbon. —  Carbon- 
ic Oxide. 

BROMINE.    Er  —  78-39. 

BROMINE  occurs  in  sea  water,  and  also  to  a  more  consid- 
erable extent  in  certain  brine  springs  both  in  America  and 
Europe.  From  these  it  may  be  obtained  by  evaporating 
the  water  until  the  salt  solution  is  concentrated,  and  after 
the  chloride  of  sodium  has  crystallized  from  the  liquor, 
passing  through  it  a  current  of  chlorine  gas,  the  solution 
turning  yellow  as  the  bromine  is  set  free.  It  is  next  agita- 
ted with  sulphuric  ether,  which  carries  to  the  surface  all 
the  bromine.  This  is  then  acted  on  by  potash,  which  gives 
a  mixture  of  bromate  of  potash  and  bromide  of  potassium. 
On  ignition,  oxygen  is  expelled,  and  the  whole  converted 
into  the  latter  salt,  from  which  the  bromine  may  be  distilled 
by  the  aid  of  peroxide  of  manganese  and  sulphuric  acid. 

It  is  a  liquid  of  a  deep  blood-red  appearance,  solidify- 
ing at  — 4°  F.,  and  boiling  at  113°  F.  Its  specific  gravity 
is  2-99.  It  exhales  an  orange  vapor,  and  is  commonly 
kept  beneath  the  surface  of  water.  Its  smell  is  very  dis 
agreeable,  a  circumstance  from  which  its  name  is  derived 
Like  chlorine,  it  bleaches,  and  in  all  its  relations  possesses 
a  general  resemblance  to  that  substance.  A  lighted  taper 
burns  for  a  short  time  in  its  vapor  with  a  greenish  flame 
Phosphorus  burns  spontaneously  in  it. 

Bromine  yields  a  hydrogen  acid  (HBr],  hydrobromic 
acid,  and  with  oxygen,  bromic  acid  (BrO^).  In  their  gen- 
eral properties  these  bodies  resemble  the  corresponding 
compounds  of  chlorine.  The  bromide  of  silver  is  much 
more  sensitive  to  light  than  either  the  chloride  or  iodide. 

.  FLUORINE,  F=  18-74, 
is  found  in  combination  with  calcium,  as  the  fluoride  of 

From  what  si  urce  is  bromine  obtained  ?  What  are  the  properties  of 
bromine,  and  to  what  bodies  has  it  a  close  analogy  ? 


238  FLUORINE. 

calcium,  or  fluor  spar.  It  occurs  also  in  the  topaz  and 
other  minerals.  In  the  enamel  of  teeth  and  in  bones  it  has 
been  detected,  especially  in  fossil  bones,  which  sometimes 
contain  as  much  as  ten  per  cent,  of  fluoride  of  calcium. 

The  special  properties  of  fluorine  are  as  yet  unknown, 
for  it  has  not  been  isolated.  Various  attempts  have  been 
made  at  different  times,  but  without  satisfactory  results. 
It  possesses  an  intense  affinity  for  electro-positive  bodies, 
and  gives  rise  to  a  series  of  compounds  resembling  those 
of  chlorine,  iodine,  &c.  It  does  not  unite  with  oxygen. 
HYDROFLUORIC  ACID.  HF=  19-74. 

This  energetic  acid  may  be  obtained  by  decomposing 
fluoride  of  calcium  by  sulphuric  acid  in  a  vessel  of  platina 
or  lead,  the  vapors  being  conducted  into  a  metallic  re- 
ceiver kept  at  a  low  temperature.     The  action  is 
CaF  +  HO,  80,...  =  .. .  CaO,  SO3  +  HF. 

It  is  a  smoking  liquid,  which  acts  powerfully  on  the 
skin,  boils  at  a  temperature  of  a  little  above  60 J  F.,  and 
possesses  the  remarkable  quality  of  corroding  glass. 

If  a  piece  of  glass  be  coated  over  with  a  thin  film  of 
bees'  wax,  and  letters  or  other  marks  made  through  the 
wax  to  the  glass  with  a  pointed  implement,  on  setting  it 
over  a  vessel  of  lead  or  tin  in  which,  from  a  mixture  of 
fluor  spar  and  sulphuric  acid,  hydrofluoric  acid  is  escaping 
in  vapor,  the  glass  is  deeply  etched  on  all  those  parts 
which  have  been  uncovered,  as  is  seen  when  the  wax  is 
removed.  Liquid  hydrofluoric  acid  may  be  employed 
for  the  same  purpose,  but  the  letters  are  not  so  visible  as 
when  the  vapor  is  used. . 

CARBON.     C  =  6-04. 

This,  which  is  one  of  the  most  interesting  and  import- 
ant of  the  elementary  bodies,  occurs  under  many  differ- 
ent natural  forms.  It  is  an  essential  ingredient  in  the 
structure  of  all  animal  and  vegetable  beings  ;  it  is  found 
in  various  states  in  the  air,  the  sea,  and  the  crust  of  the 
earth. 

The  striking  peculiarity  of  carbon,  which  at  once  arrests 
our  attention,  is  the  different  allotropic  conditions  under 
which  it  is  presented.  This  substance  may  be  said  to  yield 

Are  the  special  properties  of  fluorine  known  ?  How  is  hydrofluoric  acid 
made  ?  What  remarkable  quality  does  it  possess  ?  From  what  sources 
may  carbon  be  procured  ?  What  is  its  most  striking  property  ? 


FORMS    OF    CARBON.  239 

in  itself  a  whole  group  of  elementary  bodies.  Among 
these  might  be  enumerated,  (1.)  Diamond,  which  crys- 
tallizes in  octahedrons,  is  transparent,  incombustible,  ex- 
cept in  oxygen  gas,  and  the  hardest  body  known ;  hence 
its  use  in  cutting  glass.  (2.)  Gas-carbon,  which,  unlike 
diamond,  is  a  good  conductor  of  electricity,  and  is  opaque. 
(3.)  The  various  forms  of  charcoal,  anthracite  coal,  and 
coke.  (4.)  Plumbago,  which  has  a  metallic  lustre,  is 
opaque,  and  so  soft  and  unctuous  that  it  is  used  to  relieve 
the  friction  of  machinery.  (5.)  Lampblack,  a  powerful 
absorbent  of  light  and  heat,  and  possessing  such  strong 
affinity  for  oxygen  that  it  can  take  fire  spontaneously  in 
the  air. 

Other  forms  of  carbon  might  be  cited ;  these,  however, 
are  enough  to  establish  the  fact  that  this  single  body  fur- 
nishes varieties  which  differ  more  strikingly  from  each 
other  than  many  different  metallic  bodies. 

Charcoal  is  made  by  the  ignition  of  wood  in  close  ves  • 
sels,  the  volatile  materials  being  dissipated  and  the 
carbon  left.     The  nature  of  the  process  may  be  il- 
lustrated by  taking  a  slip  of  wood,  b,  Fig.  241,  and 
placing  its  burning  extremity  in  a  test  tube,  a.     This 
retards  the  access  of  the  surrounding  air,  and,  as  the 
combustion  proceedsj  a  cylinder  of  charcoal  is  left. 
Fig-  242.  Lampblack  is  formed  on 

a  similar  principle.  In  the 
iron  pot,  a,  Fig.  242,  some 
pitch  or  tar  is  made  to  boil, 
a  small  quantity  of  air  being  ad- 
mitted through  apertures  in  the 
brickwork.  Imperfect  combustion 
takes  place,  the  hydrogen  alone 
burning,  the  carbon  being  carried 
as  a  dense  cloud  of  smoke  into 
the  chamber  b  c  by  the  draft. 
In  this  there  is  a  hood,  or  cone,  of 
coarse  cloth,  d,  which  may  be 
raised  or  lowered  by  a  pulley.  The  sides  of  the  chamber 
are  covered  with  leather,  and  on  these  the  lampblack 
collects. 

Diamond   is  the  purest  form  of  carbon.     Its  specific 

Mention  some  of  its  allotropic  forms.  How  are  charcoal  and  lampblack 
n;adf> .' 


240  CARBONIC    OXIDE. 

gravity  is  3'5  :  it  exhibits  a  high  refractive  and  dispersive 
action  upon  light.  Charcoal  possesses,  in  consequence  of 
its  porous  structure,  the  quality  of  absorbing  many  times 
its  own  volume  of  different  gases.  Ivory  black,  which  is 
made  by  the  ignition  of  bones  in  close  vessels,  has  the  val- 
uable quality  of  removing  organic  coloring  matters  from 
their  solutions  :  a  property  which  may  be  shown  by  filter- 
ing a  solution  of  indigo  through  it.  In  all  its  forms,  car- 
bon-seems to  be  infusible,  but  when  burned  in  air  or  an 
excess  of  oxygen,  they  all  give  rise  to  carbonic  acid  gas. 
It  combines  directly  with  several  of  the  metals,  yielding 
carburets.  With  oxygen  it  gives  two  compounds, 

CO  ...  CO2, 

de^jg&ated  respectively  as  carbonic  oxide  and  carbonic 
acid. 

CARBONIC  OXIDE,  CO  =  14-053, 

is  produced  when  carbon  is  burned  in  a  limited  supply 
of  oxygen,  or  when  carbonic  acid  is  passed  over  red-hot 
iron,  or  over  red-hot  carbon.     In  these  cases  the  actions 
are: 
*  C03+C   ......  .  2(CO). 

COz+Fe  ...  —  ...  CO  +  FeO. 

In  the  first  the  carbonic  acid  unites  with  one  atom  of 
carbon,  and  yields  two  of  carbonic  oxide ;  in  the  second, 
it  loses  one  atom  of  oxygen  to  the  iron  and  yields  one  of 
carbonic  oxide.  .  It  may  also  be  prepared  by  heating  ox- 
r.  243.  alic  acid  with  oil  of  vitriol  in  a  flask, 

a,  Fig.  243,  the  decomposition  giving 
equal  volumes  of  carbonic  acid  and 
carbonic  oxide,  as  is  explained  under 
oxalic  acid.     The  acid  may  be  sepa- 
rated by  passing  the  mixture  through 
a  bottle,  b,  containing  potash  water, 
and  the  oxide  collected  over  water.     But  the  best  process 
/or  procuring  it  is  to  heat  one  part  of  prussiate  of  potash 
with  ten  of  oil  of  vitriol  in  a  retort :  the  carbonic  oxide 
comes  over  in  a  state  of  purity. 

As  obtained  by  any  of  these  processes,  it  is  a  colorless 

What  are  the  properties  of  diamond?  What  are  those  of  ivory  black? 
What  are  the  oxygen  compounds  of  carbon  ?  What  is  the  action  of  car- 
bon and  of  metallic  iron  on  carbonic  acid  at  a  red  heat?  How  is  carbonic 
txide  produced  from  oxalic  acid  ?  From  what  other  substance  may  it  be 
procured  ? 


•>..  •  :.  : 

CARBONIC    ACID.  241 

gas,  which  may  be  kept  over  water,  in  Fig.  244. 

which  it  is  only  sparingly  soluble.  It 
is  without  odor,  and  is  irrespirable.  A 
jet  of  it  burns  in  the  air  with  a  beauti- 
ful blue  flame,  combining  with  oxygen 
and  yielding  carbonic  acid.  Its  specific 
gravity  is  0*9722 :  it  has  never  been 
liquefied.  It  is  the  combustion  of  this 
gas  which  produces  the  blue  flame  oft- 
en seen  in  a  coal  fire.  Carbonic  oxide 
is  a  compound  radical,  giving  origin  to  a  series  of  bodies. 


LECTURE  LIV. 

CARBONIC  ACID. — Methods  of  Preparation  by  Decomposi- 
tion and  Combustion. — General  Properties,  and  Relation 
to  Combustion  and  Respiration. — Its  Solution  in  Water. 
— Exists  in  the  Breath. — Its  Liquid  and  Solid  Forms. 
— Light  Carbureted  Hydrogen. — Marsh  Gas.— Natu- 
ral and  Artificial  Production. — Olefiant  Gas. — Action 
with  Chlorine. 

CARBONIC  ACID.     CO*  =  23-066. 

CARBONIC  acid  is  commonly  prepared  by  the  action  of 
dilute  hydrochloric  acid  on  chalk,  or  any  carbonate  of 
lime,  the  action  being 

CaO,  CO,i-HCl  ...  =  ...  CaCl,HO+CO,; 
that  is,  one  atom  of  carbonate  of  lime  and      Fig.  245. 
one  of  hydrochloric  acid  yield  one  atom  of 
chloride  of  calcium  and  one  of  water,  and  one 
atom  of  carbonic  acid  gas  is  set  fred.     The 
process  may  be  conducted  in  a  flask,  as  in  the 
figure,  the  gas  being  evolved  so  rapidly  that 
it  may  be  collected  over  water,  though  that 
liquid  absorbs  it  very  freely. 

Carbonic  acid  is  abundantly  formed  in  many  process- 
es. It  is  the  result  of  the  complete  combustion  of  carbon- 
aceous bodies,  is  evolved  during  the  respiration  of  ani- 

What  are  the  properties  of  this  gas  ?  How  is  carbonic  acid  gas  made  ? 
Tinder  what  circumstances  is  carbonic  acid  formed  daring  combustion  7  In 
what  other  processes  does  it  appear? 

-A. 


242 


CARBONIC    ACID. 


mals,  arid  in  alcoholic  fermentation.     It  is  t\ie  fixed  air  of 
the  older  chemists. 

It  is  a  colorless  and  transparent  gas  at  common  tem- 
peratures, with  a  faint  smell  and  slightly  acid  taste.  It  is 
irrespirable,  and  acts  in  a  diluted  state  as  a  narcotic  pois- 
on ;  even  air,  containing  one  tenth  of  its  volume  of  this 
Fig.  246.  gas,  produces  a  marked  effect.  Its  specific 
gravity  is  1-527,  and  it  may,  therefore,  be 
collected  by  displacement  (Fig.  246).  For 
the  same  reason,  it  collects  in  the  bottom  of 
wells  and  pits,  and  often  suffocates  work- 
men who  descend  into  such  places.  It  does 
not  support  combustion ;  a  lighted  taper  lowered  into  a 
*  247  Jar  partly  filled  with  it  is  extinguished  the  mo- 
merit  it  reaches  the  gas  (Fig.  247).  It  may  be 
poured  from  one  vessel  to  another,  and  if  a  jar  of 
it  is  poured  upon  the  flame  of  a  candle,  the  light 
is  at  once  extinguished.  Its  density  and  other 
qualities  may  be  well  illustrated  when  it  is 
formed  by  the  action  of  fuming  nitric  acid  on 
carbonate  of  ammonia,  a  smoky  cloud  marking 
its  position  and  movements. 

Carbonic  acid  reddens  litmus  water,  but  the  blue  col- 
or is  restored  on  boiling,  the  acid 
being  driven  off  by  the  heat.  It  is 
soluble  in  water,  which,  under  in- 
creased pressure,  takes  up  several 
times  its  volume  of  it,  constituting 
the  soda  water  of  the  shops.  Its 
solubility  may  be  established  by 
agitating  it  with  water  in  Hope's 
eudiometer,  Fig.  248,  or  by  passing  it 
through  Nooth's  soda-water  machine,  Fig. 
249. 

A  common  test  for  the  presence  of  car- 
bonic acid  in  wells  is  to  lower  a  lighted 
candle,  and  if  its  flame  be  extinguished, 
it  is  inferred  that  the  gas  is  present ;  but  it  does  not  fol- 
low that  a  man  may  safely  descend  into  such  places  though 
a  candle  will  continue  to  burn. 


What  are  its  properties?  What  are  its  relations  to  combustion? 
What  is  its  specific  gravity  ?  What  is  soda  water  ?  How  may  carbonic 
acid  be  detected  ? 


CARBON    AND    HYDROGEN.  243 

If,  through  a  tube,  the  breath  be  made  to  pass  into 
lime-water,  a  deposit  of  carbonate  of  lime  renders  the 
water  milky  ;  or,  if  the  breath  be  conducted  through  lit- 
mus water,  the  color  changes  to  red  ;  the  air  thus  expired 
from  the  lungs  contains  three  or  four  per  cent,  of  carbonic 
acid. 

Under  a  pressure  of  thirty-six  atmospheres,  carbonic  acid 
condenses  into  a  liquid  characterized  by  the  extraordinary 
quality  that  it  is  four  times  more  expansible  by  heat  than 
even  atmospheric  air.  This  liquid,  when  allowed  to  es- 
cape through  a  jet,  evaporates  so  rapidly,  and  produces  so 
much  cold,  that  a  portion  of  it  instantly  solidifies.  Solid 
carbonic  acid  is  a  substance  not  unlike  snow  ;  mixed  with 
alcohol  or  ether,  it  produces  a  degree  of  cold  equal  to 
—180°  Fahr. 

Although  carbonic  acid  has  the  name  of  an  acid,  it  pos 
sesses  the  properties  indicated  by  that  term  in  a  feeble 
degree.  The  gas  contains  its  own  volume  of  oxygen. 
The  common  test  for  its  presence  is  lime-water,  which  is 
rendered  turbid  by  it. 

CARBON  AND  HYDROGEN. 

These  substances  unite,  producing  many  compounds, 
some  of  which  are  solid,  some  liquid,  and  others  gaseous*  . 
They  are  of  course  all  combustible  bodies,  and  the  de»"" 
scription  of  nearly  all  of  them  belongs  to  organic  chem 
istry. 

LIGHT  CARBURETED  HYDROGEN,  CH2  =  8-04, 
occurs  abundantly  in  coal  mines,  and  forms  with  their 
atmospheric  air  explosive  mixtures  ;  it  is  also  found  dur- 
ing the  putrefaction  of  vegetable  matter  under  wate:r  ; 
on  stirring  the  mud  of  ponds,  bubbles  of  this  gas  escape; 
hence  the  name  marsh  gas.  It  may  be  obtained  artificially 
by  heating  acetate  of  potash  with  hydrate  of  baryta. 

(KO)  +  (C<H,03)  -f  (BaO,  HO]  ...  =  ...  (KO,  CO,)  + 


that  is,  one  atom  of  acetate  of  potash  with  one  of  hy- 
drate of  baryta  yield  one  of  carbonate  of  potash,  one  of 
carbonate  of  baryta,  and  two  of  light  carbureted  hydro- 

How  can  its  existence  in  the  breath  be  proved  ?  What  are  the  proper- 
ties of  liquid  and  solid  carbonic  acid  1  What  is  the  test  for  it  1  How  may 
light  carbureted  hydrogen  be  made  1  Where  is  it  found  naturally  ? 


244 


OLEFIANT    GAS. 


gen  gas,  the  acetic  acid  being  decomposed,  by  the  aid  of 
water,  into  carbonic  acid  and  marsh  gas.  It  is  a  color- 
less gas,  burns  with  a  yellow  flame,  producing  water  and 
carbonic  acid.  Its  specific  gravity  is  0*555,  forms  explo- 
sive mixtures  with  air,  and  is  the  fire  damp  of  coal  mines. 
The  choke  damp,  which  exists  in  mines  after  an  explo- 
sion, is  carbonic  acid  gas,  originating  from  the  combustion. 
This  gas  is  decomposed  by  chlorine  in  the  light,  but  not 
in  darkness. 

OLEFIANT  GAS.     C4#4  =  28-16. 

Olefiant  gas  may  be  made  by  heating  one  part  of  alco- 
hoi  with  four  of  sulphuric  acid  in 
a  flask,  a,  Fig.  250.  The  vapor  of 
ether  which  comes  over  with  it  may 
be  removed  by  causing  the  gas  to 
pass  through  a  small  bottle,  &,  con- 
taining sulphuric  acid,  before  being 
collected  at  the  trough.  It  may  also 
be  obtained  by  an  apparatus  such  as  Fig.  251,  in  which 


Fig.  251. 


.  250. 


b  is  the  flask  containing  alcohol  and  sulphuric  acid,  and  a 
an  interposed  globe  to  receive  the  ether,  oil  of  wine,  and 
water,  which  distill  over. 

Olefiant  gas  is  transparent  and  colorless  ;  burns  with  a 
beautiful  flame  (Fig.  252,  page  245) ;  forms  an  explosive 
mixture  with  oxygen,  giving  rise  by  its  combustion  to  car- 


Of  what  does  the  explosive  gas  of  coal  mines  consist  ?     How  is  olefiact 
gas  prepared?     What  are  the  products  of  combustion  of  olefiant  gas  ? 


CYANOGEN. 


245 


bonic  acid  and  water.  If  mixed  with 
an  equal  volume  of  chlorine,  the  gases 
condense  into  an  oily  liquid,  from.which 
olefiant  gas  has  received  its  name.  With 
twice  its  volume  of  chlorine,  if  it  be  set 
on  fire,  hydrochloric  acid  is  formed,  and 
carbon  is  deposited  as  a  dense  black 
smoke. 

Olefiant  gas  also  exists  as  one  of  the 
chief  ingredients  in  the  gas  employed 
for  illuminating  cities. 


Ft*.  252. 


LECTURE  LV. 

CYANOGEN. — Modes  of  Preparation. — Liquefaction. — An 
Electro-negative  Compound  Radical.  —  Bisulphuret  of 
Carbon. — BORON. — Boracic  Acid. —  Terfluoride  of  Bo- 
ron.— SILICON. — Silicic  Acid. — Fluoride  of  Silicon. — 
Compounds  of  Hydrogen  and  Nitrogen. — Amidogen. — 
Ammonia. — Ammonium. —  Theory  of  Berzelius. 
CYANOGEN,  Cy . .  OR  BICARBURET  OF  NITROGEN.  C2JV=26'23. 
CARBON  unites  with  nitrogen,  forming  a  bicarburet, 
when  these  substances  are  in  the  nascent  state  and  in  pres- 
ence of  a  base.     It  may  be  obtained  very  easily  by  expo- 
sing the  cyanide  of  mercury  to  heat,  or  by  heating  a  mix- 
ture of  six  parts  of  ferrocyanide  of  potassium  and  nine  of 
corrosive  sublimate. 

It  is  a  colorless  gas,  having  a  peculiar  odor.  It  burns 
with  a  beautiful  purple  flame,  dissolves  readily  in  water, 
and  still  more  so  in  alcohol,  condenses  into  a  liquid  by  a 
pressure  of  3'6  atmospheres  at  45°  Fahrenheit,  as  may 
be  shown  by  heating  with  a  lamp  cyanide  of  mercury  in  a 
bent  tube,  as  seen  in  Fig.  253  ;  the  tube  pig.  253 
being  closed  at  both  ends,  liquid  cyanogen 
accumulates  at  the  cool  extremity.  Though 
a  compound  body,  it  has  all  the  properties 
and  characters  of  a  powerful  electro-nega- 
tive  element.  A  farther  description  of  it 
and  its  compounds  will  be  given  under  organic  chemistry. 

What  is  the  action  of  chlorine  on  it  ?    From  what  has  it  derived  its 
name  ?    How  is  cyanogen  made  ?    How  may  it  be  condensed  into  a  liquid  ? 

X2 


246  SULPHUR    AJCD    CARDOX. 

BISULPHURET  OF  CARBOX,  CSt  =38-28, 
may  be  made  by  passing  the  vapor  of  sulphur  over  char- 
coal ignited  in  a  tube,  and  receiving  the  product  in  a  cold 
bottle ;  the  apparatus  is  represented  in  Fig.  254.     Into 


Fig.  254. 


the  top  of  a  large  iron  bottle  two  tubes,  I  c,  one  straight 
and  the  other  bent,  are  inserted;  the  bottle  having  been 
filled  with  charcoal,  pieces  of  brimstone  are  dropped  in 
through  the  tube  b,  as  soon  as  the  bottle  is  red  hot.  The 
sulphur  and  carbon  unite.  The  product  passes  along  the 
tubes  c  fy  cooled  by  a  stream  of  water  from  the  cock,  d, 
the  water  being  conducted  by  a  string,  h,  into  a  basin,  x. 
The  vapor  passes  into  the  bottle,  n,  which  is  partially  filled 
with  ice,  and  the  incondensable  gases  pass  out  through  m. 
It  is  a  transparent  liquid  of  a  very  disagreeable  odor,  has 
the  quality  of  dissolving  sulphur  and  phosphorus,  boils  at 
108°  Fahrenheit,  and  is  therefore  very  volatile. 

BORON,  5  =  io-9, 

was  discovered  by  Davy  as  the  basis  of  boracic  acid,  from 
which  it  may  be  set  free  by  potassium  at  a  red  heat.  It 
is  an  olive-colored  solid,  which  burns  when  ignited  in  ox- 
ygen gas  or  atmospheric  air,  and  produces  boracic  acid. 

BORACIC  ACID.     BO3=  34-939. 

Boracic  acid  exists  in  the  waters  of  the  volcanic  springs 
of  Tuscany.  It  is  also  brought  from  India  combined  with 
soda,  and  may  be  artificially  procured  by  dissolving  one 

How  is  bisulphuret  of  carbon  formed  ?    From  what  is  boron  derived  ? 
How  is  boracic  acid  prepared  ? 


SILICON.  247 

part  of  borax  in  four  of  hot  water,  and  adding  half  a  part 
of  sulphuric  acid.  On  cooling,  the  boracic  acid  is  depos- 
ited in  small  crystalline  scales,  which  may  be  purified  by 
recrystallization. 

Boracic  acid  melts  at  a  red  heat  Ft^.  255. 

into  a  transparent  glass.  Its  crystals 
raised  to  212°  Fahrenheit,  lose  half 
their  water.  It  volatilizes  readily 
when  boiled  in  water,  is  soluble  in 
alcohol,  the  solution  burning  with  a 
green  flame.  The  experiment  may 
be  made  in  a  glass  instrument  like  Fig.  255,  a  b  c.  It  is 
a  very  feeble  acid,  and  even  turns  yellow  turmeric  brown, 
like  an  alkali. 

TERFLUORIDE  OF  BORON,  BF3  —  66-94, 
is  formed  when  a  mixture  of  fluor  spar,  boracic  acid,  and 
oil  of  vitriol  is  heated  in  a  flask.     It  is  decomposed  by 
water,  by  which  it  is  rapidly  absorbed.     In  damp  air  it 
forms  white  fumes. 

SILICON.    Si  =  22-18. 

This  element  may  be  prepared  by  igniting  the  silico- 
fluoride  of  potassium  with  potassium,  Fig.  256. 

acting  upon  the  resulting  substance 
with  water,  which  removes  the  fluor- 
ide of  potassium,  and  leaves  the  sili- 
con as  a  nut-brown  powder. 

It  exhibits  two  allotropic  states. 
Prepared  as  first  described,  it  takes 
fire  and  burns  when  heated  in  atmos- 
pheric air ;  but  if  previously  ignited 
in  close  vessels,  it  shrinks  in  volume, 
and,  passing  into  its  other  state,  becomes  incombustible  in 
oxygen  gas. 

SILICIC  ACID.     SiOs  =  46-219. 

Silicic  acid  is  one  of  the  most  abundant  bodies  in  na- 
ture, existing  under  the  innumerable  forms  of  the  quartz 
minerals,  sands,  and  sandstones.  Rock  crystal  and  flint 
are  pure  silicic  acid. 

It  may  be  obtained  in  a  more  convenient  form  by  fusing 

What  is  the  color  it  communicates  to  flame  ?  How  may  silicon  be  pre- 
pared ?  In  what  respect  does  it  differ  after  ignition  ?  What  is  the  con.- 
Btitution  of  silicic  acid,  and  how  may  it  be  prepared  ? 


248 


FLUORIDE    OF    SILICON. 


Fig.  257. 


white  sand  with  four  parts  of  carbonate  of  potash,  dissolv- 
ing the  resulting  silicate  in  water,  and  decomposing  the 
solution  with  hydrochloric  acid.  The  silicic  acid  sepa- 
rates as  a  gelatinous  hydrate,  slightly  soluble  in  water, 
which,  when  washed  and  dried,  yields  a  white  powder 
absolutely  insoluble  in  water.  There  is  reason  to  be- 
lieve that  the  silicon  exists  in  its  different  allotropic  states 
in  these  two  forms  of  silicic  acid. 

Silica  is  a  gritty  substance,  sufficiently  hard  to  scratch 
glass.  Its  specific  gravity  is  2'66.  It  combines  with  the 
alkalies  in  excess  to  form  glass.  It  requires  a  high  tem- 
perature for  fusion.  Hydrofluoric  acid  is  the  only  acid 
which  dissolves  it. 

FLUORIDE  OF  SILICON,  SiF3  —  78-22, 

may  be  obtained,  as  just  stated,  by  dissolving  silica  in  hy- 
drofluoric acid,  or  by  heating 
a  mixture  of  fluor  spar  and 
sand  with  sulphuric  acid.  It 
is  colorless  ;  fumes  in  the 
air ;  its  specific  gravity  is 
3*66.  Transmitted  from  the 
flask  which  generates  it,  a, 
Fig.  257,  through  water,  it 
is  decomposed,  hydrated  sil- 
ica being  deposited.  To  pre- 
vent the  tube  which  delivers 
the  gas  being  stopped  up  by 
the  silica,  some  quicksilver, 
ef  may  be  put  in  the  vessel, 
d,  and  the  tube  dipped  into 
it,  so  that  the  bubbles  of  gas 
may  not  come  in  contact  with  the  water  until  they  have 
reached  the  surface  of  the  metal  ;  the  sulphuric  acid  may 
be  introduced  through  the  funnel,  I.  In  the  water,  hydro- 
fluosilicic  acid  forms,  which  is  sometimes  used  as  a  test 
for  potash.  ;  -- 

NITROGEN  and  HYDROGEN  yield  three  compounds  : 

NH, . . .  NH3 . . .  NH4 ; 
they  are  designated  respectively  by  the  names 

What  are  its  properties  ?  When  the  fluoride  of  silicon  is  passed  through 
water,  what  are  the  products  ?  How  many  compounds  of  nitrogen  and 
hydrogen  are  admitted  ? 


AMIDOGEN.  249 

v 

Amidogen. 
Ammonia. 
Ammonium. 

AMIDOGEN.    NH2  =  16-19. 

Amidogen  is  a  hypothetical  compound  radical,  the  ex- 
istence of  which,  in  several  compounds,  is  inferred.  On 
heating  potassium  in  ammoniacal  gas,  one  third  of  the  hy- 
drogen is  set  free,  and  an  olive  substance  remains,  the 
amidide  of  potassium.  This,  in  contact  with  water,  yields 
potash  and  ammonia. 

K,  NH2  +  HO...  =  ...KO  +  NH3. 
Amidogen  is  an  electro-negative  compound  radical  like 
cyanogen. 

AMMONIA.     NH3  =  17-19. 

This  substance,  called  also  volatile  alkali,  from  its 
properties,  is  an  abundant  product  of  the  putrefaction  of 
animal  matters,  and  may  be  obtained  by  the  destructive 
distillation  of  horn  ;  hence  the  term,  spirit  of  hartshorn  : 
it  also  exists  in  the  air,  and  is  a  common  product  of  many 
chemical  reactions,: 

It  may  be  obtained  by  heating  in  a  flask,  Fig.  258. 
a,  Fig.  258,  equal  quantities  of  slacked 
lime  and  muriate  of  ammonia,  and,  as  its 
specific  gravity  is  only  O590,  it  may  be  col- 
lected, as  in  the  cut,  in  a  flask  or  jar,  b, 
with  the  mouth  downward,  by  displacing 
the  heavier  air.  The  action  is, 

(NH3  +  HCl)  +  (CaO,  HO)  ...  =  ... 
CaCl  +  2HO  +  NH3. 

It  is  a  transparent  and  colorless  gas,  of  excessive  pun- 
gency, and  having  all  the  qualities  of  a  strong  alkali.  It 
turns  turmeric  paper  brown,  is  absorbed  with  wonderful 
rapidity  by  water,  which,  at  32°  F.,  takes  up  780  times 
its  volume  of  the  gas,  a  result  which  may  be  illustrated 
by  inverting  a  flask  full  of  it  in  some  cold  water,  when  the 
water  rushes  up  with  sufficient  violence  to  destroy  the 
flask  very  frequently.  Ammonia  neutralizes  the  strongest 
acids,  as  may  be  shown  by  dropping  it  into  litmus  water 
which  has  been  reddened  by  sulphuric  or  nitric  acid. 

"What  is  amidogen?  From  what  substances  may  ammonia  be  pro- 
cured ?  What  is  its  specific  gravity  ?  "What  class  of  bodies  does  it  closely 
resemble?  How  may  its  affinity  for  water  be  illustrated?  How  does  it 
act  on  reddened  litmus  water  ? 


250 


AMMONIA. 


Fig.  259.  It  is  composed  of  three  volumes  of  hydro- 

gen with  one  of  nitrogen,  condensed  into  two 
volumes.  It  may  be  recognized  by  its  re- 
markable odor,  and  by  the  formation  of  white 
clouds  when  a  rod,  a,  Fig.  259,  dipped  in 
muriatic  acid,  is  approached  to  it.  It  con- 
denses into  a  liquid  at  60°  under  a  pressure 
of  6 '5  atmospheres. 

Its  solution  in  water,  known  as  aqua  ammonias,  is  pre- 
pared by  passing  the  gas  evolved  from  slacked  lime  and 
sal  ammoniac  through  Wolfe's  bottles,  as  is  represented 
in  Fig.  260  ;  the  water  will  take  it  up  until  its  specific 

Fig.  260. 


gravity  is  lowered  to  0-872  ;  it  then  contains  32£  per 
cent,  of  gas.  This  solution,  somewhat  diluted,  is  much 
used  by  chemists  for  neutralizing  and  precipitating.  It 
also  affords  the  best  means  of  obtaining  ammonia,  mere- 
ly requiring  to  be  warmed  in  a  flask,  when  the  gas  read- 
ily comes  off. 

AMMONIUM,  Am  =  NH*  =  18-19, 

is  a  hypothetical  body,  and  believed  to  be  of  a  metallic 
nature  ;  its  symbol  is,  therefore,  Am.  It  may  be  combined 
with  mercury  by  decomposing  a  solution  of  an  ammoni- 
acal.salt  by  a  Voltaic  current,  the  negative  pole  being  in 
contact  with  a  globule  of  that  metal,  or  by  putting  an 

What  is  its  constitution  ?  How  may  it  be  detected  ?  By  what  pro- 
cess is  aqua  ammonioe  made  ?  What  is  the  nature  of  ammonium  ?  In 
what  state  may  it  be  obtained  ? 


AMMONIUM.  251 

amalgam  of  potassium  and  mercury  in  water  of  ammonia. 
Under  these  circumstances,  the  mercury  swells,  and  event- 
ually becomes  of  a  soft  consistency  like  butter,  preserving 
its  metallic  aspect  completely.  All  attempts  to  separate 
the  ammonium  from  this  amalgam  have  failed.  It  decom- 
poses into  NH3  and  //. 

It  is  now  generally  agreed  by  chemists  that  ammonium 
is  the  basis  of  the  salts  of  ammonia.  Thus,  sal  ammoniac, 
called  also  the  muriate  of  ammonia,  is  NH3  +  HCl;  but 
this  is  evidently  the  same  as  NH4  -f-  Cl,  that  is,  the  chlo- 
ride of  ammonium.  In  all  cases  where  ammonia  forms 
neutral  salts  with  the  so-called  oxygen  acids,  it  requires  an 
atom  of  water,  but  this  water  evidently  gives  it  the  con- 
stitution, not  of  NH3  -f-  HO,  but  NH4  +  O  ;  the  water, 
therefore,  makes  it  oxide  of  ammonium,  which  will  unite 
with  sulphuric,  or  nitric,  or  any  other  acid,  precisely  after 
the  manner  of  any  other  metallic  oxide.  Moreover,  the 
compounds  of  ammonia  with  this  atom  of  water  are  iso- 
morphous  with  the  compounds  of  the  oxide  of  potassium. 
From  these  facts,  therefore,  we  see  that  when  sulphuric 
acid  unites  with  ammonia,  the  atom  of  water  which  the 
ucid  contains  gives  to  the  salt  the  constitution 

NH»  O  +  S03,  °r  ^-#4  +  SO4,  or  Am  +  SO4, 
the  latter  formula  being  analogous  to  Am  +  Cl,  the  chlo- 
ride of  ammonium  or  sal  ammoniac.     This  view  of  the  na- 
ture of  the  ammonia  compounds  is  known  under  the  name 
of  the  ammonium  theory  of  Berzelius. 

Of  the  compounds  of  ammonium  with  other  bodies,  the 
protosulphuret,  NH^  <S,  may  be  mentioned  under  the 
name  of  hydrosulphuret  of  ammonia.  It  is  much  used  as 
a  test.  There  are  also  other  sulphurets. 

How  can  it  be  shown  that  it  is  the  base  of  the  ammonia  salts  ?  What 
is  meant  by  the  ammonium  theory  of  Berzelius  T 


THE  METALS, 


LECTURE  LVI. 

GENERAL  PROPERTIES  OF  THE  METALS. — Definition  of  a 
Metal. — Color,  Specific  Gravity,  Hardness,  Tenacity, 
and  other  Properties. — Relations  to  Heat. —  Compounds 
with  other  Bodies. — Division  into  Groups. —  The  Oxides 
and  their  Reduction. —  The  Sulphurets  and  their  Reduc- 
tion. 

OF  the  elementary  bodies, by  far  the  larger  portion  are 
metallic.  By  a  metal  we  mean  a  body  which  possesses 
that  peculiar  manner  of  reflecting  light  which  is  known 
under  the  designation  of  metallic  lustre.  It  is  also  a  good 
conductor  of  electricity  and  heat.  Of  these  there  are  at 
least  forty-two,  and  probably  forty-five,  three  having  been 
recently  discovered. 

Most  of  the  metals  are  of  a  white  color,  but  they  differ 
from  each  other  by  slight  shades,  some  having  a  faint  blue 
and  others  a  pinkish  tint.  There  are  three  which  are  strik- 
ingly colored :  gold,  which  is  yellow,  and  copper  and  ti- 
tanium, which  are  red.  In  specific  gravity  they  differ  ex- 
ceedingly; potassium  is  so  light  as  to  float  upon  water, 
and  indium  is  twenty-one  times  as  heavy  as  that  liquid. 

Many  of  the  metals  are  malleable,  that  is,  can  be  ex- 
tended into  thin  sheets  under  the  blows  of  a  hammer ; 
others  are  so  brittle  that  they  may  be  reduced  to  powder 
in  a  mortar ;  some  of  them  are  ductile,  and  may  be 
drawn  into  fine  wires,  the  order  for  malleability  not  being 
the  same  as  that  for  ductility.  Thus,  iron  may  be  drawn 
into  fine  wire,  but  can  not  be  beaten  out  into  such  thin 
sheets  as  many  other  metals.  Of  all  metals  gold  is  the 
most  malleable,  and  platina  has  been  drawn  into  the  finest 
wires. 

What  is  the  definition  of  a  metal?     How  many  metals   are  there? 
What  is  their  color  commonly?     Which  three  are  the  colored  metals? 
Of  the  metals,  which  is  the  lightest,  the  heaviest,  the  most  malleable,  the 
softest,  the  hardest,  the  most  fusible,  and  the  most  volatile  ? 
252 


PROPERTIES    OF    THE    METALS. 


253 


In  hardness  the  metals  differ  much.  Potassium  is  so 
soft  that  it  may  be  moulded  by  the  fingers,  but  iridium  is 
among  the  hardest  bodies  known.  In  tenacity  or  strength 
the  same  differences  are  seen :  of  all  metals  iron  is  the 
most  tenacious.  The  same  metal  differs  very  much  in 
this  respect  at  different  temperatures. 

In  their  relations  to  heat,  well-marked  distinctions  also 
may  be  traced.  Mercury  at  all  ordinary  temperatures  is 
in  a  melted  condition ;  but  platina  can  only  be  fused  be- 
fore the  oxyhydrogen  blow-pipe.  As  inspects  volatility, 
mercury,  cadmium,  potassium,  sodium,  zinc,  arsenic,  and 
tellurium,  may  be  distilled  or  sublimed  at  a  red  heat. 

The  metals  unite  with  electro-negative  bodies,  and  with 
each  other.  In  decomposition  by  the  Voltaic  battery,  they 
pass  to  the  negative  pole,  and  are,  therefore,  described  as 
electro-positive  bodies.  Their  compounds  with  oxygen, 
chlorine,  &c.,  pass  under  the  names  of  oxides,  chlorides, 
&c.;  their  compounds  with  each  other  under  the  name  of 
alloys,  or,  if  mercury  be  present,  of  amalgams.  They  also 
unite  with  sulphur,  phosphorus,  and  carbon. 

Chemical  writers  usually  divide  the  metals  into  groups 
founded  upon  their  relations  with  oxygen  gas.  The  fol- 
lowing simple  division  is  the  one  I  adopt :  1st.  Metals 
which  decompose  water  at  common  temperatures ;  2d. 
Metals  which  can  not  decompose  water  at  common  tem- 
peratures, but  do  it  at  a  red  heat ;  3d.  IV^etals  which  can- 
not decompose  water  at  all. 

1st  Group 


Potassium. 

Sodium. 

Lithium. 

Barium. 

Strontium. 

Calcium. 

Magnesium. 

3d  Group. 

Aluminum. 

Glucinum. 

Thorium. 

Yttrium. 

Zirconium. 

Lanthanum. 


enum. 
Manganese. 
Iron. 
Nickel. 
Cobalt. 
Zinc. 

admium. 
Tin. 

3d  Group. 

Chromium. 

Vanadium. 

Tungsten. 

Molybdenum. 

Osmium. 

Columbium. 


Titanium. 

Arsenic. 

Antimony. 

Tellurium. 

Uranium. 

Copper. 

Lead. 

Bismuth. 

Silver. 

Mercury. 

Gold. 

Palladium. 

Platinum. 

Rhodium. 

Iridium. 


The  older  chemists  divided  the  metals  into  four  class- 
es :   1st.  Alkaline,  such  as  potassium.     2d.  Earthy,  such 

With  what  other  substances  dp  they  unite  ?     Into  what  groups  may 
they  be  divided  ?     What  is  the  division  formerly  in  use? 

\ 


254  METALLIC    OXIDES. 

as  magnesium.     3d.  Imperfect,  as  zinc.     4th.  Noble,  as 
gold. 

THE  METALLIC  OXIDES. 

Metallic  substances  unite  with  oxygen  with  different  de- 
grees of  intensity,  and  in  very  different  proportions,  many 
of  them  giving  rise  to  a  complete  series  of  oxides,  and 
producing,  1st.  Basic  oxides.  2d.  Neutral  or  indifferent 
oxides.  3d.  Metallic  acids. 

1st.  The  basic  oxides  are  commonly  protoxides  or  seS' 
quioxides,  which  form  neutral  salts  with  hydrogen  acids, 
with  the  production  of  water.  To  form  such  salts,  for 
every  atom  of  oxygen  in  the  base  there  is  required  one 
atom  of  acid.  A  basic  protoxide,  therefore,  requires  one 
atom  of  acid,  a  sesquioxide  three,  and  a  deutoxide  two, 
to  form  a  neutral  salt. 

2d.  The  neutral,  or  indifferent,  oxides  contain  more 
oxygen  than  the  base,  and,  when  heated  with  acids,  give 
off  that  oxygen,  a  basic  oxide  resulting. 

3d.  The  metallic  acids  always  contain  more  oxygen  ; 
they  may  be  sesquioxides,  deutoxides,  teroxides,  or  quadr- 
oxides,  and  are  commonly  formed  by  deflagrating  the 
metal  with  nitrate  of  potash. 

REDUCTION  OF  THE  METALLIC  OXIDES. 

Some  of  the  oxides,  such  as  those  of  mercury,  silver, 
and  gold,  may  be  reduced  by  heat  alone  ;  but  the  great- 
er number  require  the  conjoint  action  of  carbon,  which, 
at  a  high  temperature,  decomposes  them  with  evolution  of 
carbonic  oxide.  Among  powerful  reducing  agents  may 
be  mentioned  the  formiates  and  the  cyanide  of  potassium, 
the  former  acting  through  the  affinity  of  carbonic  oxide 
for  oxygen,  and  the  latter  through  the  affinity  of  carbon 
and  potassium  conjointly.  The  deoxydation  of  metals  may 
also  be  accomplished  by  reducing  agents,  such  as  phos- 
phorous and  sulphurous  acids,  or  by  the  action  of  other 
metals  ;  iron,  for  instance,  will  precipitate  metallic  copper 
from  its  solutions. 

The  Voltaic  current  affords  a  powerful  means  of  ef- 
fecting the  reduction  of  metals  in  philosophical  investiga- 
tions ;  by  its  aid  the  alkaline  metals  were  originally  ob- 
tained. The  electrotype,  already  described,  is  an  exam- 

What  substances  do  metals  yield  with  oxygen  ?     How  are  metallic  acids 
commonly  made  ?     By  wh«t  processes  may  metallic  oxides  be  reduced  , 


METALLIC    SULPHURETS.  255 

pie  of  its  action  ;  even  solutions  of  metallic  salts  are 
readily  decomposed  by  it.  Thus,  if  a  Fig,  sei. 

glass  jar,  T,  Fig.  261,  be  divided  into 
halves,  and  a  paper  diaphragm  be  in- 
troduced between  them,  the  halves  being  B| 
tightly  pressed  together  by  the  ring  B  B, 
if  the  jar  be  filled  with  any  metallic  so- 
lution, such  as  the  sulphate  of  soda,  and 
the  positive  and  negative  wires  of  the 
battery  dipped  in  the  opposite  compartments,  after  a  time 
the  metallic  oxide  will  be  found  in  one  of  them  and  the 
acid  in  the  other,  a  total  decomposition  having  taken  place. 

THE  METALLIC  SULPHURETS. 

Many  of  these,  such  as  the  sulphurets  of  iron,  lead,  and 
copper,  are  found  abundantly  in  nature ;  or  they  may  be 
made  artificially  by  heating  the*  metal  with  sulphur,  or  by 
deoxydizing  metallic  sulphates  by  charcoal  or  hydrogen 
gas,  which  converts  them  into  sulphurets ;  or  by  the  ac- 
tion of  sulphureted  hydrogen  on  their  oxides,  which  yields 
a  metallic  sulphuret  and  water.  From  their  solutions 
under  these  circumstances,  iron,  manganese,  zinc,  cobalt, 
and  nickel  can  not  be  precipitated,  though  they  may  by 
hydrosulphuret  of  ammonia. 

The  sulphurets  of  a  metal  are  usually  equal  in  num- 
ber, and  similar  in  constitution  to  its  oxides ;  and  as  ox- 
ygen compounds  unite  with  each  other  to  produce  oxygen 
salts,  the  sulphurets,  in  like  manner,  also  unite  with  each 
other  to  produce  sulphur  salts. 

REDUCTION  OF  THE  SULPHURETS. 
The  metallic  sulphurets  may  often  be  reduced  by  melt- 
ing them  with  another  metal  having  a  more  powerful  af- 
finity for  sulphur ;  thus,  iron  filings  will  decompose  sul- 
phuret of  antimony,  sulphuret  of  iron  forming,  and  anti- 
mony being  set  free.  On  the  large  scale,  however,  a 
different  process  is  resorted  to ;  the  sulphuret,  by  roast- 
ing, is  converted  into  a  sulphate,  much  of  the  sulphur 
being  expelled  during  the  process  as  sulphurous  or  sul- 
phuric acid.  The  resulting  sulphate  is  then  acted  upon 

'  By  what  processes  may  metallic  sulphurets  be  obtained?  What  metals 
can  not  be  precipitated  by  sulphureted  hydrogen  ?  What  relation  exists 
between  the  sulphurets  and  oxides  ?  How  are  the  sulphurets  reduced  ? 
What  is  the  process  on  the  large  scale  ? 


256  POTASSIUM. 

by  lime  and  carbon  at  a  high  temperature ;  the  lime  de- 
composes the  sulphate,  setting  free  the  metallic  oxide, 
which  is  at  once  reduced  by  the  carbon,  the  sulphate  of 
lime  turning  simultaneously  into  the  sulphuret  of  calci- 
um, which  floats  on  the  surface  of  the  metal  as  a  slag. 

The  metals  also  unite  with  chlorine,  iodine,  bromine, 
carbon,  phosphorus,  &c.,  and  some  with  hydrogen  and 
nitrogen.  These  compounds  will  be  described  in  theii 
proper  places. 


LECTURE  LVII. 

POTASSIUM. — Discovery  of,  and  Properties. — Relations  to 
Oxygen  and  Water. — Its  Oxides. — Caustic  Potash. — 
Tests  for  Potash. — Haloid  Compounds  of  Potassium. — 
Salts  of  the  Protoxide,  the  Carbonate,  Nitrate,  Chlorate, 

SfC. 

POTASSIUM.    X  =  39-15. 

POTASSIUM  was  first  obtained  by  Sir  H.  Davy,  who  de- 
composed its  hydrated  oxide  (potash)  by  a  Voltaic  cur- 
rent. From  the  positive  pole  oxygen  gas  escaped  in  bub- 
bles, and  metallic  potassium  in  globules  appeared  at  the 
negative. 

It  was  subsequently  discovered  that  the  same  sub- 
stance could  be  decomposed  by  iron,  and  also  by  carbon 
at  a  high  temperature  ;  and  the  latter  of  these  substances 
is  now  exclusively  resorted  to  for  the  preparation  of  po- 
tassium. The  carbonate  of  potash  is  ignited  with  char- 
coal in  an  iron  bottle,  and  the  potassium  received  into  a 
vessel  containing  naphtha.  The  productiveness  of  the  op- 
eration is  greatly  interfered  with  by  the  circumstance 
that  the  carbonic  oxide  which  is  evolved,  as  it  cools  be- 
low a  red  heat,  unites  with  much  of  the  potassium,  pro- 
ducing a  gray  substance,  which  chokes  the  tubes  smd 
diminishes  the  yield  of  the  metal. 

Potassium  is  a  bluish  white  metal,  which,  at  32°  F'.,  is 
brittle,  melts  at  150°  F.,  and  boils  at  a  red  heat,  yielding 
a  green  vapor.  Its  specific  gravity  is  '865  ;  it  is,  there- 
Prom  what  was  potassium  first  obtained?  What  process  is  now  in 
use  for  its  preparatkra  1  What  circumstance  interferes  with  the  produc- 
tiveness of  this  pr.c-jss  ?  What  are  the  properties  of  potassium? 


OXIDES    OF    POTASSIUM.  257 

fore,  much  lighter  than  water,  on  the  surface  of  which  it 
floats.  At  70°  F.  it  may  be  moulded  by  the  fingers,  be- 
ing soft  and  pasty. 

It  possesses  an  intense  affinity  for  oxygen, 
and  hence  requires  to  be  preserved  in  bot- 
tles containing  naphtha.  A  piece  of  it  thrown 
upon  water  takes  fire,  and  burns  with  a  beau- 
tiful pink  flame.  In  the  air  it  speedily  tar- 
nishes, and,  even  when  brought  in  contact 
with  ice,  it  decomposes  it  with  the  evolution  of  flame.  In 
these  cases  the  combustion  arises  from  the  hydrogen  unit- 
ing with  the  oxygen  of  the  air  and  reproducing  water ; 
the  potassium  simultaneously  burns. 

POTASSIUM  AND  OXYGEN. 

There  are  two  oxides  of  potassium,  a  protoxide  and  a 
peroxide, 

KO...KO3. 

The  affinity  of  potassium  for  oxygen  is  so  great  that  it  takes 
that  substance  from  almost  all  other  bodies,  and  hence  is 
used  as  a  powerful  deoxydizing  agent. 

Protoxide  of  Potassium.     KO  =  47-163. 
This  substance  can  only  be  formed  by  the  action  of  po- 
tassium on  dry  air  or  oxygen.     It  possesses  a  great  affin- 
ity for  water,  and  is  converted  by  it  into  the  hydrated  ox- 
ide of  potassium,  commonly  called  caustic  potash. 

Hydrated  Oxide  of  Potassium.     KO,  HO  =  56-176. 

This  substance  is  best  procured  by  boiling  two  parts  of 
pure  carbonate  of  potash  with  twenty  of  water,  and  hav- 
ing previously  slacked  one  part  of  quicklime  with  hot  wa- 
ter, the  cream  which  it  forms  is  to  be  added  by  degrees, 
and  the  whole  boiled.  The  process  should  be  conducted 
in  an  iron  vessel  to  which  a  lid  can  be  adapted,  so  as  to 
exclude  the  air  during  cooling ;  the  resulting  carbonate 
of  lime  settles  perfectly,  and  the  hydrate  may  be  obtained 
by  evaporating  the  solution  rapidly  in  a  silver  vessel,  pour- 
ing out  the  melted  residue  on  a  silver  plate,  or  casting  it 
into  the  form  of  small  cylinders. 

The  decomposition  which  takes  place  in  the  foregoing 
process  is  simple, 

How  many  oxides  does  it  form  ?  How  is  the  hydrated  oxide,  or  caustic 
potash,  obtained  ?  What  is  the  nature  of  the  decomposition? 

Y2 


258  OXIDE3    OF    POTASSIUM. 

KO,  CO,,  +  CaO,  HO ...  =  ...  CaO,  CO,  +-  KO, HO / 

that  is,  the  lime  takes  carbonic  acid  from  the  carbonate  of 
potash,  and  the  oxide  of  potassium  unites  with  water.  The 
solution  may  be  known  to  be  free  from  carbonic  acid  by 
not  effervescing  when  mixed  with  stronger  acids. 

The  hydrate  of  potash  is  a  white  solid,  having  a  power- 
ful affinity  for  water,  and  abstracting  it  rapidly  from  the 
air.  Taken  between  the  fingers,  it- communicates  to  the 
skin  a  soft  feel,  and,  if  a  concentrated  solution  be  used, 
soon  effects  a  disorganization;  hence  it  is  used  by  sur- 
geons in  the  form  of  small  sticks  as  an  escharotic.  It 
possesses  pre-eminently  the  alkaline  qualities,  and,  indeed, 
may  be  taken  as  the  type  of  that  class  of  bodies,  neutral- 
izes the  most  powerful  acids  perfectly,  and  communicates 
to  turmeric  paper,  or  turmeric  solution,  a  brown  tint.  It 
turns  the  infusion  of  rea  cabbage  green,  and,  possessing 
an  intense  affinity  for  carbonic  acid,  is  used  in  organic 
analysis  to  absorb  that  gas. 

Potash  in  combination  occurs  in  all  fertile  soils,  and  is 
essential  to  the  growth  of  land  plants,  from  the  ashes  of 
which  its  carbonate  is  abundantly  procured.  This  may  be 
shown  by  filtering  water  through  the  ashes  of  wood,  when 
the  clear  liquid  will  be  found  to  answer  to  all  the  tests  in- 
dicating the  presence  of  potash.  It  occurs  also  abundant- 
ly in  feldspar,  and  hence  is  found  in  clays.  The  want  of 
fertility  in  soils  appears  occasionally  to  be  due  to  the  ab- 
sence of  this  body. 

The  bichloride  of  platinum  gives,  with  a  solution  of 
potash,  a  yellow  precipitate  of  the  chloride  of  platinum 
and  potassium.  When  the  amount  of  potash  is  small,  it 
is  well  to  add  alcohol  at  first,  in  which  the  double  chlo- 
ride is  insoluble.  Ammonia  yields  a  similar  precipitate  j 
but  this  may  be  avoided  by  exposing  the  substance,  in  the 
first  instance,  to  a  red  heat  before  testing.  Perchloric  acid, 
with  alcohol,  yields  a  white  precipitate.  Tartaric  acid, 
if  added  in  excess,  and  the  mixture  stirred  with  a  glass 
rod,  bearing  gently  on  the  sides  of  the  vessel,  gives  white 
streaks  of  the  bitartrate  -of  potash  wherever  the  rod  has 
passed  over  the  glass. 


Of  what  properties  is  the  hydrate  of  potash  possessed,  and  what  are  its 
uses  ?  How  may  the  existence  of  potash  in  the  ashes  of  plants  be  proved  T 
What  are  the  tests  for  the  presence  of  this  substance  ? 


COMPOUNDS    OF    POTASSIUM.  259 

Of  other  compounds  of  potassium,  the  following  may  be 
mentioned  : 


Peroxide  of  potassium,  K Os. 
Chloride  of  potassium,  KCl. 
Iodide  of  potassium,  K.I. 


Bromide  of  potassium,  KBr. 
Protosulphuret  of  potassium,  KS. 
Pentasulphuret  of  potassium,  KS$. 


It  also  combines  with  hydrogen  in  two  proportions,  pro- 
ducing a  solid  and  a  gas,  the  latter  of  which  takes  fire 
spontaneously  in  the  air. 

Of  these  compounds,  the  most  important  are  the  per- 
oxide of  potassium,  which  is  formed  by  passing  oxygen 
over  red-hot  potash ;  it  is  decomposed  by  water,  evolving 
oxygen  and  producing  potash  ;  the  chloride  of  potassium, 
which  is  analogous  to  common  salt;  the  iodide,  much  of 
which  is  consumed  in  medicine,  under  the  name  of  hy- 
driodate  of  potash.  It  may  be  prepared  by  dissolving 
iodine  in  a  solution  of  potash,  till  the  liquid  begins  to  ap- 
pear brown,  then  evaporating  to  dryness,  and  igniting  the 
residue  :  oxygen  is  evolved,  and  iodide  of  potassium  re- 
mains ;  it  may  be  then  dissolved  in  water,  and  crystal- 
lized. It  is  white,  crystallizes  in  cubes,  and  is  very  sol- 
uble in  water  and  hot  alcohol.  Its  solution  will  dissolve 
large  quantities  of  iodine.  The  pentasulphuret-is  the  chief 
ingredient  of  liver  of  sulphur,  which  is  formed  by  fusing 
sulphur  with  carbonate  of  potash  at  a  low  temperature. 

SALTS  OF  THE  PROTOXIDE  OF  POTASSIUM. 

Carbonate  of  Potash  is  obtained  by  lixiviating  the  ashes 
of  plants.  In  an  impure  state  it  forms  the  potashes  and 
pearlashes  of  commerce.  It  may  be  obtained  pure  by  ig- 
niting the  bitartrate  with  half  its  weight  of  the  nitrate  of 
potash.  It  has  an  alkaline  taste,  its  solution  feels  greasy 
to  the  fingers,  it  is  very  soluble  in  water,  and  deliquescent. 

Bicarbonate  of  Potash,  formed  by  transmitting  a  stream 
of  carbonic  acid  through  a  solution  of  the  former  salt.  It 
crystallizes  in  eight-sided  prisms  with  dihedral  summits. 

Sulphate  of  Potash,  formed  by  neutralizing  the  follow- 
ing salt.  Crystallizes  in  anhydrous,  oblique,  fo«r-sided 
prisms,  soluble  in  about  ten  times  its  weight  of  water. 

Sulphate  of  Potash  and  Water,  sometimes  designated 
as  the  bisulphate  of  potash  ;  it  is  the  residue  of  the  produc- 
tion of  nitric  acid.  It  is  soluble  in  water,  and  has  an  acid 
reaction.  It  crystallizes  in  rhombohedrons. 

Name  some  of  its  other  compounds.  What  are  the  properties  of  the 
iodide  ?  From  what  is  the  carbonate  obtained  ? 


260  SALTS    OF    POTASH. 

Nitrate  of  Potash  is  extracted  on  the  large  scale  from 
certain  soils  in  which  organic  matter  is  decaying  in  con- 
tact with  potash.  It  crystallizes  in  six-sided  prisms,  fuses 
at  a  heat  beneath  redness,  with  evolution  of  oxygen  gas. 
It  is  soluble  in  about  three  times  its  weight  of  water,  at 
common  temperatures.  This  salt  enters  as  an  essential 
ingredient  in  gunpowder,  which  is  composed  of  about  one 
atom  of  nitrate  of  potash,  one  of  sulphur,  and  three  of 
carbon.  The  sulphur  of  this  mixture  accelerates  the  com- 
bustion, while  the  oxygen  of  the  nitre  forms  carbonic  acid 
with  the  charcoal.  The  products,  therefore,  of  the  per- 
fect combustion  of  gunpowder  are  carbonic  acid,  nitrogen, 
and  the  sulphuret  of  potassium.  It  commonly  happens, 
however,  that  sulphate  of  potash  is  formed.  The  pro- 
portions of  the  ingredients  of  gunpowder  are  varied  for 
different  uses.  The  powder  used  for  mining,  for  exam- 
ple, contains  more  sulphur  than  that  used  for  firearms. 

Chlorate  of  Potash. — When  a  stream  of  chlorine  is 
passed  into  a  solution  of  potash,  the  chloride  of  potassium 
and  the  chlorate  of  potash  result;  the  latter  is  deposited 
in  flat,  scaly  crystals. 

The  chlorate  of  potash  contains  no  water ;  it  dissolves 
in  about  fifteen  times  its  weight  of  that  fluid ;  melts  at  a 
red  heat,  with  evolution  of  pure  oxygen  ;  deflagrates  with 
combustible  bodies,  sometimes  with  much  violence. 


LECTURE  LVIII. 

SODIUM. — Preparation  of. — Relation  to  Oxygen  and  W^a- 
ter. — Color  communicated  to  Flame. — Its  Oxides. —  The 
Hydratcd  Oxide. —  Tests  for  Sodium. — Haloid  Com- 
pounds.— Common  Salt. — Salts  of  the  Protoxides,  Car- 
bonates,  Sulphates,  Nitrates,  fyc.  LITHIUM. — BARIUM. 
— It^  Oxides. — 'Haloid  Compounds. — Salts  of  the  Pro- 
toxide. 

SODIUM.    ATa  =  23-3. 

SODIUM  may  be  obtained  by  the  same  process  as  potas- 
sium, but  is  best  procured  by  igniting  the  calcined  acetate 
of  soda  with  powdered  charcoal  in  an  iron  bottle ;  and,  as 

What  is  the  origin  and  use  of  the  nitrate  ?  How  is  the  chlorate  made  7 
How  is  sodium  obtained,  and  what  are  its  uses  ? 


OXIDES    OF    SODIUM.  261 

the  sodium  does  not  act  upon  carbonic  oxide,  the  opera- 
tion is  much  more  productive  than  in  the  case  of  the  oth- 
er metal.  Like  potassium,  it  is  to  be  kept  in  bottles  un- 
der the  surface  of  naphtha. 

In  color,  sodium  resembles  silver ;  its  specific  gravity  is 
0-9348  ;  it  therefore  floats  upon  water.  It  melts  at  194° 
F..  and  is  more  volatile  than  potassium.  Thrown  upon 
water,  it  decomposes  it  with  a  hissing  sound,  and  with  the 
evolution  of  hydrogen,  but  no  flame  appears.  If,  howev- 
er, the  water  is  hot,  then  a  beautiful  yellow  flame,  char- 
acteristic of  sodium  and  its  compounds,  is  the  result. 
SODIUM  AND  OXYGEN. 

With  oxygen  sodium  forms  three  compounds  :  the  sub- 
oxide,  protoxide,  and  peroxide. 

Protoxide  of  Sodium.     NaO  =  31-313. 

This,  like  the  corresponding  potassium  compound,  is 

produced  by  oxydizing  sodium  in  dry  air.     It  is  a  white 

powder,  which  attracts  moisture  from  the  air  and  forms  the 

hyd  rated  oxide  of  sodium,  commonly  called  caustic  soda. 

Hydrated  Oxide  of  Sodium,  NaO  +  HO  =  40-323, 
or  caustic  soda,  may  be  made  by  the  same  process  as  that 
given  for  caustic  potash,  by  using  carbonate  of  soda,  and, 
when  the  resulting  carbonate  of  lime  has  settled,  evapo- 
rating the  liquid.  The  best  proportions  are  one  part  of 
quicklime  to  five  of  carbonate  of  soda  in  crystals. 

Caustic  soda  resembles  caustic  potash  in  most  of  its 
properties.  It  is  deliquescent,  has  a  strong  affinity  for 
carbonic  acid,  and  acts  upon  animal  tissues  as  an  escha- 
rotic.  Its  salts  are  generally  more  soluble  than  the  pot- 
ash salts,  and  on  this  are  founded  the  methods  recom- 
mended for  distinguishing  the  latter  compounds  from  it. 
Moreover,  the  soda  compounds  communicate  to  the  flame 
of  alcohol,  or  to  the  blow-pipe  flame,  a  yellow  color :  the 
same  tint  which  is  characteristically  seen  when  sodium 
is  placed  in  hot  water. 

Chloride  of  Sodium.     NaCl  —  58-77. 
The  chloride  of  sodium,  common  salt,  is  obtained  abund- 
antly from  the  waters  of  the  sea,  to  which  it  gives  their 

What  are  its  properties  compared  with  potassium  ?  What  compounds 
with  oxygen  does  it  give  ?  How  is  caustic  soda  obtained?  What  are  its 
properties  and  uses  ?  What  color  do  the  sodium  compounds  give  to  flame  ? 


262  CHLORIDE    or    SODIUM. 

salinity.  It  is  also  found  as  rock  salt,  deposited  exten- 
sively in  certain  geological  formations. 

Common  salt  is  the  general  type  of  that  extensive  class 
of  compounds  which  have  derived  the  name  of  salt  bodies 
from  it.  It  crystallizes  in  cubes,  and,  when  in  mass,  is 
often  perfectly  transparent,  and  permits  the  passage  of 
heat  of  every  temperature  through  it  freely.  It  melts  into 
a  liquid  at  a  red  heat,  crystallizes  in  cubes,  and  is  not 
more  soluble  in  hot  than  cold  water.  It  is  extensively 
used  in  the  preparation  of  hydrochloric  acid  and  chlo- 
rine ;  immense  quantities,  also,  are  annually  consumed  in 
the  preparation  of  carbonate  of  soda,  which  is  made  by 
first  acting  on  the  common  salt  with  oil  of  vitriol,  so  as  to 
turn  it  into  sulphate  of  soda,  and  igniting  this  with  char- 
coal and  carbonate  of  lime  :  an  impure  carbonate  of  soda 
is  the  result,  known  under  the  name  of  black  ash,  or  Brit- 
ish barilla.  Common  salt  is  extensively  used  for  the 
curing  of  meat.  It  is  also  an  essential  article  of  food, 
being  decomposed  in  the  animal  system,  and  furnishing 
hydrochloric  acid  to  the  gastric  juice  and  soda  to  the  bile. 

The  compounds  of  sodium  with  bromine,  iodine,  sul- 
phur, &c.,  are  not  of  interest. 

SALTS  OF  THE  PROTOXIDE  OF  SODIUM. 
Carbonate  of  Soda  is  sometimes  obtained  by  lixiviating 
the  ashes  of  sea-weeds.  Large  quantities  are  also  pro- 
cured from  the  decomposition  of  sulphate  of  soda  by  saw- 
dust and  lime  at  a  high  temperature,  the  carbonaceous 
matter  decomposing  the  sulphuric  acid  and  generating 
carbonic  acid,  which  unites  with  the  soda,  while  the  liber- 
ated sulphur  is  partly  dissipated  and  partly  unites  with 
the  calcium.  From  the  resulting  mass  carbonate  of  soda 
is  obtained  by  lixiviation.  The  crystals,  as  found  in  com- 
merce, contain  generally  ten  atoms  of  water ;  there  are 
two  other  varieties,  the  one  containing  eight  atoms,  and 
the  other  one  atom  of  water.  Large  quantities  of  the 
carbonate  of  soda  are  also  sold  in  an  uncrystallized  state, 
under  the  name  of  salts  .of  soda.  The  figure  of  the  crys- 
tals of  this  salt  is  a  rhombic  octahedron.  They  effloresce 
on  exposure  to  the  air.  They  are  soluble  in  five  times 

What  is  the  constitution  of  common  salt  ?  From  what  sources  is  it  de- 
rived ?  What  are  its  properties  ?  How  is  barilla  obtained  from  it  ? 
Why  is  it  essential  as  an  article  of  food  ?  From  what  source  is  the  car- 
bonate  of  soda  obtained  ?  Describe  the  preparation  of  it  from  the  sulphate. 


fALTS    OF    SODA. 

their  weight  of  cold  and  in  less  than  their  own  weight  of 
boiling  water. 

Bicarbonate  of  Soda,  or  the  double  carbonate  of  soda 
and  water,  is  formed  by  transmitting  a  stream  of  carbonic 
acid  through  a  solution  of  the  carbonate,  and  is  in  the 
form  of  a  white  powder.  It  is  less  soluble  in  water  than 
the  former.  There  is  a  sesquicarbonate,  which  passes  in 
commerce  under  the  name  of  trona. 

Sulphate  of  Soda  is  the  Glauber's  salt  of  the  shops  ;  oc- 
curs as  a  natural  product,  and  also  as  the  result  of  the 
preparation  of  hydrochloric  acid.  It  is  in  prismatic  crys- 
tals of  a  bitter  taste,  efflorescing  in  the  air,  and  becoming 
anhydrous.  .Water  dissolves  more  than  half  its  weight 
of  this  salt  at  911°  F.,  but  above  that  degree  it  is  less  sol- 
uble. When  a  solution  of  three  parts  of  this  salt  in  two 
parts  of  water  is  corked  up  in  a  flask  while  boiling,  it  may 
be  cooled  without  crystallization  taking  place  ;  but  if  the 
cork  is  withdrawn,  crystallization  commences  at  once,  or 
if  it  does  not,  the  introduction  of  any  solid  matter  produ- 
ces it,  and  the  temperature  of  the  solution  at  once  rises. 

Nitrate  of  Soda  is  found  abundantly  in  different  parts 
of  America  in  the  soil ;  it  crystallizes  in  rhomboids,  dis- 
solves in  twice  its  weight  of  cold  water,  and,  from  its  del- 
iquescence, can  not  be  used  in  the  manufacture  of  gun- 
powder. 

Phosphate  of  Soda  (tribasic)  is  formed  by  neutralizing 
phosphoric  acid  with  carbonate  of  soda ;  two  of  the  hy- 
drogen atoms  are  replaced  ;  it  crystallizes  in  oblique 
rhombic  prisms,  dissolves  in  three  times  its  weight  of  cold 
water,  is  of  an  alkaline  taste,  and  gives  a  lemon-yellow 
precipitate  with  nitrate  of  silver.  By  the  addition  of  soda 
to  it  a  subphosphate  is  formed,  in  which  all  three  of  the 
hydrogen  atoms  of  the  acid  are  replaced  ;  but  by  the  ad- 
dition of  phosphoric  acid  to  the  ordinary  phosphate,  till  it 
ceases  to  give  any  precipitate  with  chloride  of  barium,  the 
biphosphate  of  soda  results,  a  salt  very  soluble  in  water. 
Its  crystals  are  rhombic  prisms.  In  it  only  one  of  the  hy- 
drogen atoms  is  replaced. 

Microcosmic  Salt,  or  the  phosphate  of  soda,  ammonia, 

What  is  the  commercial  n#me  of  the  sulphate  ?  What  peoiliarity  is 
there  ia  the  crystallization  of  its  solution  ?  Why  can  not  the  nitrate  be 
used  for  gunpowder?  What  is  the  difference  between  the  phosphate, 
the  pyrophosphate,  and  the  metaphosphate  of  soda  ? 


264  LITHIUM. 

and  water,  is  made  by  dissolving  seven  parts  of  phosphate 
of  soda  in  two  parts  of  water,  and  adding  one  part  of  sal  am- 
moniac. At  a  low  heat  it  parts  with  its  water  of  crystal- 
lization, and  the  temperature  rising,  it  loses  its  ammonia 
and  saline  water,  becoming  monobasic  phosphate  of  soda. 
It  is  much  used  in  blow-pipe  experiments. 

Pyrophosphate  of  Soda  (bibasic)  is  procured  by  heating 
the  phosphate.  It  gives  a  white  precipitate  with  nitrate 
of  silver. 

Metaphosphate  of  Soda  (monobasic)  is  formed  by  heat- 
ing microcosmic  salt  to  redness.  It  is  soluble  in  water, 
melts  at  a  red  heat,  and  gives,  with  dilute  solutions  of  the 
earthy  and  metallic  salts,  viscid  precipitates. 

-  Biborate  of  Soda,  the  borax  of  the  shops.  It  is  import- 
ed in  a  crude  state  from  the  East  Indies,  and  manufac- 
tured from  the  natural  boracic  acid  of  Italy  by  the  addi- 
tion of  carbonate  of  soda.  It  crystallizes  in  octahedrons, 
or  in  oblique  prisms,  the  former  containing  five,  the  latter 
ten  atoms  of  water,  all  of  which  is  lost  by  exposure  to  a 
red  heat,  the  salt  then  fusing  into  a  glass.  It  is  of  great 
use  in  blow-pipe  experiments. 

LITHIUM.     Z,  =  642. 

This  rare  metal  occurs  in  certain  minerals,  such  as 
epodumene,  lepidolite,  &c.  It  is  a  white  metal,  commu- 
nicating to  flame  a  red  color.  It  yields'  a  protoxide  the 
carbonate  of  which  is  of  sparing  solubility  in  water ;  thus 
forming  the  link  of  connection  between  the  potash  and 
soda  carbonates,  which  are  very  soluble,  and  the  carbon- 
ates of  the  alkaline  earths,  as  baryta  and  strontia,  which 
are  insoluble. 

This  brings  us'to  the  metals  of  the  alkaline  earths,  which 
form  a  division  of  our  first  group  ;  the  first  of  these  is 

BARIUM.    Ba  =  68-7. 

The  existence  of  barium  was  first  proved  by  Davy,  who 
isolated  it  by  electrifying  mercury  in  contact  with  the  hy- 
drate of  baryta,  an  amalgam  formed,  from  which  the  mer- 
cury was  subsequently  distilled,  leaving  the  barium  as  a 
metal  of  a  grny  color  like  cast  iron,  heavier  than  sulphuric 
acid,  in  which  it  sinks,  obtaining  oxygen  rapidly  from  the 

"What  is  microcosmic  salt  ?  From  what  source  is  borax  derived,  and 
what  are  its  uses  ?  In  what  minerals  does  lithium  occur?  What  is  the 
relation  of  its  carbonate  to  those  of  the  preceding  and  subsequent  metals  I 
How  was  barium  first  obtained  ? 


OXIDES    OF    BARIUM.  265 

air,  and  giving  rise  to  the  production  of  the  protoxide  of 
barium,  baryta. 

Protoxide  of  Barium,  BaO  =  76-713, 
may  be  obtained  by  igniting  the  nitrate  of  baryta,  the  de- 
composition being 

BaO,  NO,  ...  =  ...  BaO  +  NO4  +  O; 
that  is,  one  atom  of  nitrate  of  barytes  yields  one  of  pro- 
toxide of  barium,  and  one  of  nitrous  acid  and  one  of  oxy- 
gen gas  are  expelled. 

This  protoxide  is  a  white  colored  body,  possessing  a 
strong  affinity  for  water,  with  which  it  exhibits  the  phe- 
nomenon of  slacking,  as  is  the  case  to  a  less  extent  with 
lime,  heat  being  evolved.  It  has  an  acrid  taste,  is  soluble 
in  water,  and  absorbs  carbonic  acid  from  the  air.  Its 
specific  gravity  is  about  4'000.  Its  soluble  salts  are  pois- 
onous. 

Hydrate  of  Baryta,  BaO,  HO  =  85-726, 
is  formed  by  slacking  the  protoxide,  and  is  a  white  pow- 
der, very  soluble  in  hot,  but  less  so  in  cold  water,  yield- 
ing, therefore,  crystals  when  a  hot  solution  cools :  these 
containlline  atoms  of  water  of  crystallization.  The  cold 
solution  is  used  as  a  test  for  carbonic  and  sulphuric  acids, 
with  which  it  forms  insoluble  white  precipitates. 

This  solution  is  most  easily  obtained  by  calcining  the 
native  sulphate  with  pulverized  charcoal,  which  converts 
it  into  the  sulphuret  of  barium.  To  a  boiling  solution  of 
this  body  oxide  of  copper  is  added  till  the  liquid  ceases  to 
blacken  a  solution  of  acetate  of  lead.  On  being  filtered, 
the  solution  of  hydrate  of  barytes  is  obtained. 

Peroxide  of  Barium,  BaO2  =  84'7, 

is  made  by  igniting  chlorate  of  potash  with  barytes,  or  by 
passing  oxygen  over  barytes  in  a  red-hot  tube.  It  is  used 
in  the  preparation  of  peroxide  of  hydrogen. 

Of  the  other  compounds  of  .barium,  the  chloride  is  much 
used  as  a  test  for  sulphuric  acid ;  it  may  be  made  by  de- 
composing carbonate  of  baryta  by  hydrochloric  acid.  The 
sulphuret  of  barium  is  made  by  igniting  the  sulphate  of 

"What  is  the  process  for  obtaining  the  protoxide,  and  also  its  hydrate? 
What  acids  is  a  solution  of  baryta  used  to  detect  ?  How  is  the  peroxide 
made  ?  "What  is  its  use  ?  For  what  purpose  is  the  chloride  of  barium 
employed  ? 

z 


"»•<•  MTItUN'i'lUM. 

LI,  huuvy  Mp.n.  \\nli  cliunuMil,  which  dooxydixoH  both 
i!i.  M  I  p!  in  1  1.  ,K  nl  in  ii  I  (ltd  bury  tu.  1  1  diNNolvoN  in  hot  \vu- 
tor,  mid  from  thin  solution  n  >!uimu  of  cuuntio  biiiyiu 
niiiy  bo  nhluinod  by  boiling  with  llm  oxiduit  of  loud  or 

rn|>|>fi.   iiinl   ;.i'|i,ii  .il  III",   lln-  HulphlirotH  "I    tllONO  lllOtlllN    by 

lillnilion,      By  acting  upon  it  with  hydrochloric.  or  nitric 
acid,  ill--  .  iil.'M.I.   or  mi  i  .id-  of  burytu  luuy  !•••  prepared. 


:-,  \|/|',l  in-1   1'imTUXIhK   OK   Ii  Mill   M 
('<it/"»i<i(<-  <>/'  Ihtrt/fd   IN  ibtind   imtivo,  UN  ilu>   ininnrul 

WitheHtt*   mid  iniiy  bd  prepared  by  prdolpitating  iiNolu 
bio  null  of  biirytu  with  mi  iilknlino  (Mirbonuto.     It  IN  NO!II- 
blo  iu  4!)()U  timM  iti  Wpiglit  of  cold  wutor,  und  XJ.'HX)  of 
boiling  vvutor. 

tiuijiJutfr  ttf  Haryta,  ibund  nutivo  iibuiuliiiitly  a«  hrany 
fi/>in  ,  und  iVoin  it  mi.,-,  i  of  tho  OOtOttOUndl  of  Curium  uro 
tH'wpurod,  It  in  cullod  huiivy  npur,  HH  douNity  lining  4f-17. 
It  cryHtnlli/oN  gonomlly  in  tubular  pluton,  und  in  wholly 
in  wutor. 


IJOCJTUllK  LIX. 

STUONTHTM.  —  U*c»  in  P-yrotroJiny.  —  Malta  of  Protoxide.—  , 
CALCIUM.—  Protoxide  vj\  —  Sourcct  in  Naturr*—  2V#/« 
j\trt  —  Unfold  Cofkpounii,  CMondvt  Wuoridct  <SV/»/f<//-- 
r/*,  9fc.—Salt*  of  the  ProtQttMti  Cat'/tonatc,  »S'////'//  »//«•, 
PJtM/i/ifttt,  Chloride.  —  MA4NC1IUNU  —  /'/v^o./'/W^.  —  Stiltt 
of  Protoxide,  Cat'botHtte,  N«//>/i</^',  ihmbfo  Pko9i>lnitf. 

—  Aiii/MiNi'M.  —  SuyuitwicUt—'UMt  in  the  Aft*.  —  7V.\7.v. 

—  Salt*  of  the  *SV,v;/«/V>.nWr,  ])oul*le  tfuljt/iatv,  Alum.  — 
Alttnu/iti'tttrt  of  Porcelain  and  (flitM.—Ot/trr  Mr.tals. 

HTJIONTITIM.     /?*•«•  43-», 

fl'n  IN  inotul  inuy  b«  ubtuinod  by  tho  wainn  jirocoHHOK 
\vhirh  hiivo  IHMMI  unod  for  obtutnitig  buriuiri,  with  \vhich 
it  him  u  oonfidePlble  urrulo^y,  It  M  nuini  -il  conipoundn  uro 
tho  Hul|ihiito  und  ourbonuto,  from  which  its  otltmr  prvpurn- 
tiotlM  ni.ty  bo  oblninctl, 

Strontiuin  yiohln  n  protoxide,  which  'in  tho  IMIIUH  of  u 
of  Hulls,  dillri  in!-   from  burytu  Htilta  in   not  being 


How  inny  tlio  mili'luii.'  nl  ImrvU'H  l»«»  I'Onvorlwd  Into  tl»'  »ul|iliur«t  (»( 
iwrlum?  Wlml  MW  tUi<  |ini|inril(Hl  nl1  tlio  I<III-|N  .....  tu  mul  ...il|.l..i  .....  i  l.» 
rvtu?  In  wltnl  IVN|MV|  iliM'i  Hltvnliniii  illU'iM'  IVulil  Inu'luni  'f 


cAi.ru  M 

|.,.i  mi  MI  <        I'll.'   <  lil. MI, IP    .iii.l   mii.ii.     HIT    H   ,-,!   in   |,N  ,,, 

llM'llllN     l"l     ill"    |»ll  I  "•:•««    •.!',- inillli,     (III,..    (,,    II.  im,.    .,    I,,  ,11 

ion)  mniHon  color.      Tim  rod  lim  of  llioin.,      ,  ..niuiiiM  llio 
I. ill. -i-  Null,  mid   llm    IOIMMM',   il'  diriNidvi'd   in    iilcnli..!,  com- 

.nnn:.-:ii,<M  io  iiH  lluiiHt  ilio  r.liuructofiiitio  tout  ol'tho  Hlron- 
i milt  ootnpoundii 

MAI/I'M  «>l<fTIIK  J'KOTOMDIC  OK  HTIIONTIH  M 
( \iiln>n<ih'  t>l'^tn>ntiti  in  llm  .\ht>n(ittuil<-  <>!'  tniiu  i  .il"-  i   i 
i^ul nltdtt*  of  tftt'otitid.    in    llm  n'/i'n/i/K1    o!'  iiiuuM'iilo^iHlM. 

It    in  not  N»  IK  M\  \    .IM  milpliiiln  of  liiirylu,  niul  in  Miiio!  to  Im 

Hollllllo    ill    llhoill      IIMIII    linn         ||;l    \Vi<li>lll    .  .  I    I  ..  .  1 1 1  MI{   Wllttll'. 

filtrate  ttf  tftrtmttti  ionim  DM  iiigrudicint  of  tint  rod  firo 

ii  <  .1    in   ihcni  i  I'M  ;    ii    <  i  \  ,i  ,i Ih  .•<•     in   ortiilmdroiiN,  mid   in 

H.illlhln   in    liv   IIIIM-M   i!  .   \\  i  p-lil   iif  .  ..I.I    \\  .il.  i    .iii.l    Ii  ill    il  ( 

wtMghi  ••!' lioiling  wttttir. 

0 ALOIUM,    Ca  m  OO'fl. 

(  '  \i  rii  \i  li.n  n<  \.  i  lin<Miohlniiiod  in  i|iiiinliiiim  NiiU'n  i.  nr 

to  |><  Mini  M  lull  <\ .limn. ii i< I  ii^  pi'oiMirl icirt.     It.  oxydi- 

zt)H  with  rapidity,  yielding  u  protoxido,  known  ulno  UK 
•  lull  I.  hum  or  lima. 

Limn  ...  .  in  «  UN  a  cnrlwnntn  in  tlm  vnrioun  li»uoi»tonpl, 
miirl)l«  .  ,  h  ilkn,  &c,,  whirli  lorm  in  miiiiy  countrUn  ox» 

toilMivr  ill. MM, I. nil  rilli-v  ••  Il  "lli,  i  .ill  .,i.  \«i  y  .il.im.l 
mil 

l''rom  thn  rurboiiiifn,  jmrn  or  oiiiflJiiim  nmy  Im  nit. 
tfiiimd  liy  nxpoHiiro  to  u  liri^lit  rod  ntntt.  1 1' llm  IIIIK^IOIIO 
contHiiiN  Hilicrt,  it  may,  liowovor,  bo  <;w/7>w/v//,  n,  wilic-nio 
nfTmin  liii'iuiii^,  which  jirovtuitH  tlio  product  from  h,  I  u,  • 

II  |M.  (  .-.-I  ;i  rilroni'  ulliiiily  I'm  \V(il«T,  nn.l  iiiiih-M  Him,' 
\\iili  \\iili  .1  "i.-.ii  rlnviitiuii  of  tdinporiUuro,  IIH  nxliiliilnd 
in  tho  prociiHN  <»l  f.l.i.  l.iii!-.  l'!\  |m  .<•<!  l«»  ;i  Im-li  l,Miip«t  ;t  • 

inn,   it     (.I.-,   j.l .  «••!    Mpl»Mi,li,lly.      Tim    I.    .h  .1,     wliirli 

I..MII  \\  IK  ii  I  inn  -I  '.  :  l.i.  I  <  .1  I  u  lnl<  .  il  ci  ,•«  il  u  I  ill  •  to  II,  in.,  I  I 
,-M«-nl  in  WMlni  ;  .in.l  il  I  i  i.  in. u  klll'lc  lli.il  i  ..I.I  \\  ltl(  i 
d'lHNolV()M  HUM  Ii  nun  <•  lli.in  liol.  I  ,  im.  \\  ,il<-i  in  «•<  >l<  .1  |.  , 
,  •!'  :i  1 1  u  I  1.1 1 1  \  «  .in  I  i.  l.i  I.  •.  in  nl  i  .ih  /.  .i.i.l  |.<  i  |',«c|  |y,  I'M, 

:.| >    IM   i  , -,l,  I, -I  if,  I   III  mir-.    Hi    M  Mf   (Mil  Of,        1 1    IM   llMnd   UN  Ii 

Irrtl.  lor  ciulMHiic,  acid,  vvilli   \\  In.  1 1   1 1    fivi       1 1  if  u  liiif  rnr. 

Wlml.  IM  thn  itiliir  H  • ttiN  !••  HuiiinT     Whtil,  im«  Mitt  iiilu»«nili»K- 

I.  nl    Illllll. 'M   nf     l; I nl.      Mill!    Nlllj.l.  .1.     '.I       Mil?        VVlllll,    ir,    In,..     ' 

Uli,|,U' wliul.  I'linnn  «l...      .1  '   I.IIPI    '       I1  i. ....  ill I i,     I,. 

Unit*  l>n  | ,1  /     \vi.ui  HI  Hi.    ,,„  ,,|  win. 'i   on  il.  I     VVIitiL  uro  tll« 

,,!,:,,,  Mi,  ,,  ..I   Im..    \vnli-rY 


268  COMPOUNDS    OF    CALCIUM. 

bonate  of  lime.  Cream  of  lime  is  nothing  but  lime-water 
in  which  hydrate  of  lime  is  mechanically  suspended.  The 
hardening  of  lime  mortars  depends  chiefly  on  the  absorp- 
tion of  carbonic  acid.  Hydraulic  lime  possesses  the  qual- 
ity of  setting  under  water.  It  contains  oxide  of  iron, 
alumina,  and  silica. 

Lime  is  best  detected  by  oxalate  of  ammonia,  with 
which  it  gives  a  white  precipitate  of  oxalate  of  lime,  pro- 
vided the  solution  be  not  acid. 

Among  other  compounds  of  calcium  may  be  mentioned 

Chloride  of  Calcium,  CaCl=55'97, 

formed  by  dissolving  carbonate  of  lime  in  hydrochloric 
acid,  evaporating  the  solution  to  a  sirup,  and,  on  cooling, 
the  chloride  crystallizes.  It  is  exceedingly  deliquescent. 
Chloride  of  calcium,  dried  without  crystallization,  is  used 
in  organic  analysis  for  collecting  water,  and,  generally,  in 
other  chemical  operations  for  drying  gases. 

Fluoride  of  Calcium,  CaF=39'24:, 

called,  also,  fluor  spar,  and  frequently  found  as  a  mineral 
associated  with  lead.  Crystallizes  in  cubes,  octahedrons, 
&c.,  of  various  colors.  It  is  found  in  fossil,  and,  to  a 
smaller  extent,  in  recent  bones.  It  is  used  for  various  or- 
namental purposes,  and  is  the  source  from  which  the  com- 
pounds of  fluorine  are  derived. 

Sulphuret  of  Calcium,  CaS=:36'Q2. 

obtained  by  igniting  the  sulphate  of  lime  with  charcoal, 
and  constitutes  Canton's  phosphorus,  commonly  made  by 
igniting  oyster  shells  with  sulphur ;  possesses  the  curious 
quality  of  shining  in  the  dark,  after  a  brief  exposure  to 
the  sun  or  to  the  rays  of  an  electric  spark. 

SALTS  OF  THE  PROTOXIDE  OF  CALCIUM. 
Carbonate  of  Lime  is  abundantly  found  in  nature,  form- 
ing whole  ranges  of  mountains,  the  limestones,  marbles, 
&c.,  of  mineralogists.  It  occurs  pure  in  the  form  of  Ice- 
land spar,  in  rhomboidal  crystals,  possessed  of  double  re- 
fraction. It  is  dimorphous,  assuming  the  form  of  six-sid- 
ed prisms,  as  in  the  mineral  called  Arragonite.  It  is  an- 

What  is  milk  of  lime  ?  For  what  purposes  is  the  chloride  of  calcium 
used  ?  Under  what  forms  does  fluoride  of  calcium  occur  ?  What  sinsu- 
lar  quality  does  the  sulphuret  of  calcium  possess  ?  What  are  the  dimor- 
phous forms  of  carbonate  of  lime  ?  ^  > 


MAGNESIUM.  269 

hydrous,  insoluble  in  wate*,  but  in  water  charged  with 
carbonic  acid  it  is  soluble,  and  is  deposited  from  such  a 
liquid  on  boiling,  or  by  the  diffusion  of  carbonic  acid  into 
the  air.  The  carbonic  acid  is  expelled  from  this  salt  by 
a  red  heat,  and  the  action  of  the  more  powerful  acids. 
Carbonate  of  lime  may  be  obtained  in  union  with  water, 
by  boiling  hydrate  of  lime  with  a  solution  of  sugar. 

Sulphate  of  Lime  —  Gypsum  —  occurs  native,  both  in 
crystals,  the  primary  form  being  a  rhombic  prism,  and  also 
in  extensive  crystalline  masses.  '.It  contains  two  atoms  of 
water  ;  there  is  a  variety,  however,  passing  under  the  name 
of  anhydrite,  which  contains  no  water.  On  calcining  the 
hydrous  sulphate  of  lime  at  a  low  red  heat,  it  becomes  plas- 
ter of  Paris,  and  has  the  property  of  setting  into  a  hard 
mass  when  made  into  a  paste  with  water.  The  sulphate 
of  lime  is  soluble  in  500  parts  of  boiling  water,  and  often 
occurs  in  the  water  of  springs,  to  which  it  communicates 
hardness. 

Phosphate  of  Lime  —  Bone-ear  tJi  Phosphate  —  is  one  of 
the  tribasic  phosphates  ;  it  is  precipitated  when  earth  of 
bones  is  dissolved  in  muriatic  acid,  and  the  solution  neu- 
tralized by  ammonia. 

Chloride  of  Lime  —  BleacJiing  Powder  —  is  made  b.y  ex- 
posing hydrate  of  lime  to  chlorine.  It  is  a  white  pow- 
der, exhaling  a  faint  odor  of  chlorine,  and  is  used  exten- 
sively as  a  bleaching  agent. 

MAGNESIUM.     Mg  =  127. 

MAGNESIUM  may  be  procured  by  igniting  a  mixture  of 
chloride  of  magnesium  and  sodium  in  a  porcelain  cruci- 
ble ;  the  chloride  of  sodium  forms,  and  magnesium  is  set 
free.  The  chloride  may  be  dissolved  by  water. 

It  is  a  white,  malleable  metal,  which  melts  at  a  red 
heat,  and,  with  excess  of  air,  oxydizes,  forming 

Protoxide  of  Magnesium  .     Mg  O  =  2  0  •  7  1  3  . 
This  substance,  called,  also,  calcined  magnesia,  or  sim- 
magnesia, may  be  made  by  heating  the  carbonate  to 
w  redness  ;  the  carbonic  acid  is  driven  off,  and  the  mag- 
nesia remains  as  a  white  powder,  insoluble  in  water,  but 

Under  what  circumstances  is  it  soluble  in  water  ?  Under  what  forms 
does  sulphate  of  lime  occur,  and  for  what  purposes  is  it  used  ?  In  what 
does  the  phosphate  of  lime  occur  ?  What  is  bleaching  powder  ?  How  is 
magnesium  obtained  ?  "What  are  the  propeities  of  it  ?  Under  what  names 
does  the  protoxide  pass  ? 

Z  2 


ply 
lo 


270  SALTS    OF    MAGNESIUM. 

neutralizing  acids  completely  and  forming  with  them  a 
complete  series  of  salts. 

Magnesia  occurs  very  abundantly  in  nature,  often  asso- 
ciated as  a  carbonate  with  carbonate  of  lime,  as  in  dolo- 
mitic  limestone.  It  also  occurs  in  fertile  soils,  and  is  es- 
sential to  the  growth  of  certain  plants. 

It  is  well  distinguished  from  all  the  foregoing  alkaline 
earths  by  the  relation  of  its  sulphate.  The  sulphates  of 
baryta,  strontia,  and  lime  form  a  series  of  salts,  the  solu- 
bility of  which,  in  water,  is  constantly  increasing ;  to 
these  the  corresponding  magnesia  salt  may  be  added  ;  it 
is  very  soluble. 

Magnesia  is  precipitated  from  its  sulphate  by  the  caus- 
tic alkalies,  and  by  the  carbonates  of  potash  and  soda  as 
a  carbonate,  but  not  by  the  carbonate  of  ammonia  in  the 
cold.  It  may  be  detected  by  adding  carbonate  of  ammo- 
nia and  phosphate  of  soda  in  succession,  when  the  phos- 
phate of  magnesia  and  ammonia  is  precipitated.  Heated 
before  the  blow-pipe,  after  having  been  moistened  with 
nitrate  t)f  cobalt,  magnesia  becomes  of  a  pinkish  color. 
SALTS  OF  THE  PROTOXIDE  OF  MAGNESIUM. 

Carbonate  of  Magnesia  is  found  native,  and  may  be 
prepared  by  boiling  the  sulphate  with  an  alkaline  carbon- 
ate, diffusing  the  precipitate  in  water,  and  passing  a 
stream  of  carbonic  acid  through  it ;  by  spontaneous  evap- 
oration the  carbonate  of  magnesia  is  deposited  in  crystals 
The  carbonate  of  magnesia,  the  magnesia  alba  of  the 
shops,  is  prepared  by  precipitating  the  sulphate  of  mag- 
nesia with  the  carbonate  of  potash  ;  it  occurs  in  light 
white  cubical  cakes,  or  in  powder,  and  is  not  a  true  car- 
bonate, for  it  does  not  contain  a  full  equivalent  of  carbonic 
acid.  It  is  said  to  be  a  compound  of  one  atom  of  hydrate 
of  magnesia  with  three  atoms  of  hydrated  carbonate  of 
magnesia.  It  is  very  slightly  soluble  in  water. 

Sulphate  of  Magnesia — Epsom  Salts  of  commerce — is 
produced  by  the  action  of  dilute  sulphuric  acid  on  magne- 
sian  limestone.  Its  crystals  are  small  four-sided  prisms, 
soluble  in  an  equal  weight  of  cold  and  three  fourths  their 
weight  of  boiling  water,  the  solution  having  a  bitter  taste. 
A.  low  heat  expels  six  out  of  the  seven  equivalents  of  the 
combined  water. 

What  is  dolomitic  limestone  ?  How  may  magnesia  be  detected  ?  How 
is  its  carbonate  prepared  ?  Of  what  is  Epsom  salt  composed  ? 


ALUMINUM.  271 

Phosphate  of  Magnesia  and  Ammonia,  one  of  the  vari- 
eties of  urinary  calculus,  may  be  formed  artificially  when 
a  tribasic  phosphate,  a  salt  of  ammonia,  and  a  salt  of  mag- 
nesia are  mixed  together. 

Magnesium  is  the  last  of  the  alkaline  earthy  metals.  Its 
history  completes  that  of  our  first  group  of  metallic  bodies. 
At  the  head  of  the  second  group  we  find  aluminum,  the 
first  of  the  earthy  metals. 

ALUMINUM.    ^^13-7. 

Obtained,  by  Wholer,  by  the  action  of  sodium  on  the 
chloride  of  aluminum,  being  the  same  process  as  that 
given  for  the  preceding  metal. 

It  is  a  gray  powder,  which  melts  beneath  a  red  heat ; 
takes  fire  when  heated  in  air,  producing 

Sesquioxide  of  Aluminum.     AIZO3=51'539. 

This  oxide,  called,  also,  alumina  and  clay,  occurs  nat- 
urally under  certain  forms,  which  are  highly  prized,  as  the 
ruby  and  sapphire.  In  a  more  impure  condition  it  yields 
the  various  common  clays,  which  also  contain  silica  or 
metallic  oxides,  or  other  extraneous  bodies. 

Alumina  may  be  prepared  from  the  sulphate  of  alumina 
and  potassa,  common  alum,  by  precipitating  the  sulphuric 
acid  by  chloride  of  barium.  The  sulphate  of  baryta  goes 
down,  and  there  is  left  in  the  solution  chloride  of  po- 
tassium and  chloride  of  aluminum.  When  the  mass  is 
dried,  water  is  decomposed  ;  hydrochloric  acid  is  then  ex- 
pelled, and  alumina,  mixed  with  the  chloride  of  potassium, 
remains  behind  ;  the  latter  is  to  be  dissolved  away  by  wa- 
ter, leaving  the  alumina  as  a  white  substance,  which,  with 
water,  forms  a  plastic  mass,  capable  of  being  moulded, 
and  retaining  its  shape  when  baked.  After  ignition,  it 
adheres  to  the  tongue,  and  during  the  act  of  drying  it  con- 
tracts considerably  in  volume,  a  property  which  formerly 
gave  rise  to  the  invention  of  Wedgewood's  pyrometer. 

The  presence  of  alumina  gives  to  the  clays  those  prop- 
erties which  fit  them  for  the  purpose  of  the  potter  and 
brickmaker.  Alumina  is  also  used  as  a  mordant  to  fix  the 
colors  of  certain  dyes  upon  cloth. 

In  what  form  is  the  phosphate  of  magnesia  and  ammonia  sometimes 
found  ?  How  is  aluminum  prepared  ?  What  is  the  constitution  of  its  ox- 
ide ?  Under  what  natural  forms  does  it  occur  ?  How  may  alumina  be 
prepared?  What  principle  is  involved  in  Wedgewood's  pyrometer? 
What  is  meant  hy  a  mordant  ? 


272  PORCELAIN. EARTHEN-WARE. GLASS. 

Alumina  is  precipitated  from  its  solutions  by  fixed  al- 
kalies, which  yield  a  white  hydrate  of  alumina,  soluble  in 
an  excess  of  the  precipitant.  It  is  also  thrown  down  by 
alkaline  carbonates ;  and,  when  these  precipitations  are 
made  in  a  solution  tinged  with  coloring  matter,  the  alu- 
mina carries  it  down  with  it.  Such  colored  precipitates 
pass  under  the  name  of  lakes  ;  and  it  is  this  property  of 
attaching  such  colors  to  itself,  enabling  it  to  cause  their 
firm  adhesion  to  cloth  fibre,  which  is  the  principle  of  its 
application  as  a  mordant. 

Among  the  purposes  to  which  alumina  is  applied  may 
be  mentioned  the  manufacture  of  PORCELAIN,  and  the  dif- 
ferent kinds  of  earthen-ware.  The  former  substance,  first 
made  by  the  Chinese,  is  very  compact  and  translucent. 
It  consists  essentially  of  clay  mixed  with  a  fusible  body, 
which  binds  all  its  parts  together,  and  is  covered  with  a 
glaze,  which  does  not  terminate  abruptly  on  the  surface, 
but  pervades  the  substance  of  the  mass.  In  this  respect 
it  differs  from  common  earthen-ware.  Feldspar,  or  the 
silicate  of  lime,  are  bodies  suitable  for  communicating  this 
glassy  structure. 

In  the  manufacture  of  porcelain,  great  care  is  taken  to 
select  clay  free  from  iron.  It  is  mixed  with  powdered 
quartz  and  feldspar,  and  the  requisite  shape  given  it  either 
by  the  potter's  wheel,  or  by  pressing  it  into  moulds.  It 
is  then  dried  in  the  air,  and  more  perfectly  in  a  furnace, 
and,  when  ignited,  forms  biscuit.  This  is  dipped  in  the 
glaze,  suspended  in  water,  and  becomes  covered  over  with 
a  uniform  coat  of  it.  It  now  remains  to  dry  it  once  more, 
and  fuse  the  glaze  upon  it. 

EARTHEN-WARE  consists  of  a  white  clay  mixed  with  sil- 
ica. It  is  glazed  with  a  fusible  material  containing  oxide 
of  lead,  and  colored  of  different  tints  by  metallic  oxides  ; 
for  example,  blue  by  cobalt. 

Connected  with  the  manufacture  of  pottery,  may  also 
be  mentioned  the  manufacture  of  GLASS,  of  which  there 
are  several  varieties,  some  consisting  of  silica,  potash  or 
soda,  and  lime,  others  containing  a  large  quantity  of  oxide 
of  lead.  If  silica  be  heated  with  carbonate  of  potash  and 
lime,  or  oxide  of  lead,  carbonic  acid  is  expelled,  and  glass 

How  may  the  presence  of  alumina  be  recognized  ?  What  are  lakes  ? 
What  substances  are  used  in  the  preparation  of  porcelain  and  earthen 
ware  ?  How  \»  glass  made  ? 


SALTS    OF    ALUMINUM.  273 

forms.  The  mass  is  kept  in  a  fused  condition  till  it  is  free 
from  air  bubbles,  and  is  then  cooled  until  it  becomes  plas- 
tic, so  that  it  may  be  blown  or  moulded. 

Articles  of  glass,  after  they  are  manufactured,  require 
to  be  annealed  or  slowly  cooled  down.  This  allows  their 
parts  to  assume  a  regular  structure,  and  prevents  excess- 
ive brittleness. 

Soluble  glass  is  formed  when  silica  is  heated  with  twice 
its  weight  of  carbonate  of  soda  or  potash.  It  derives  its 
name  from  the  fact  that  it  is  for  the  most  part  soluble  in 
water. 

SALTS  OF  THE  SESGUJIOXIDE  OF  ALUMINUM. 

Sulphate  of  Alumina  is  made  by  dissolving  alumina  in 
dilute  sulphuric  acid.  It  enters  into  the  composition  of 
the  alums. 

Sulphate  of  Alumina  and  Potash — Alum. — This  import- 
ant salt  is  prepared  from  alum  slate.  It  crystallizes  in 
octahedrons,  has  an  astringent  taste,  reddens  litmus  paper. 
It  dissolves  in  about  eighteen  times  its  wreight  of  cold,  and 
less  than  its  own  weight  of  boiling  water.  It  contains 
twenty-four  atoms  of  water,  and,  when  exposed  to  heat, 
foams  up,  melting  in  its  own  water,  which,  being  evapo- 
rated away,  leaves  a  white  porous  mass,  commonly  called 
burnt  alum. 

In  the  same  way  that  the  sulphate  of  potash  unites  with 
the  sulphate  of  alumina,  so,  also,  do  the  sulphates  of  am- 
monia and  of  soda,  forming  respectively  the  ammoniacal 
and  soda  alums.  The  alumina  in  the  common  alum  may 
be  replaced,  also,  by  the  sesquioxides  of  iron,  manganese, 
or  chromium,  giving  iron,  manganese,  and  chrome  alums. 

The  following  metals,  GLUCINUM,  THORIUM,  YTTRIUM, 
ZIRCONIUM,  LANTHANIUM,  and  CERIUM,  are  very  rare  bod- 
ies, and,  being  of  little  interest,  may  be  passed  over  with- 
out farther  notice. 

Why  mast  it  be  annealed  ?     What  are  the  properties  of  the  sulphate 
of  alumina  and  poUash  ? 


274  MANGANESE. 


LECTURE  LX. 

MANGANESE. — Its  Seven  Oxides. —  The  Peroxide  and  its 
Applications. —  Mineral  Chameleon. — Acids  of  Manga- 
nese.— Salts  of  the  Protoxide. — IRON. — Its  Natural 
Forms. — Reduction  on  the  Great  Scale. — Cast  Iron. — 
Wrought  Iron. — Steel. — Passive  Iron. 

MANGANESE.    jtf»  =  27-7. 

MANGANESE  may  be  procured  by  igniting  its  oxides  with 
a  mixture  of  lampblack  and  oil  in  a  powerful  furnace,  the 
reduction  being  somewhat  difficult.  It  is  a  white  metal, 
specific  gravity  8'013,  requiring  a  white  heat  for  its  fusion, 
and  oxydrzing  readily  in  the  air.  It  is  remarkable  for  the 
number  of  oxygen  compounds  which  it  yields ;  they  are 
MnO  .  .  .  Mn,Oz .  .  .  MnO,  .  .  .  MnO8  .  .  .  Mn^O,  .  .  . 


designated  respectively, 

Protoxide  of  manganese. 
Sesquioxide  of  manganese. 
Peroxide  of  manganese. 


Permanganic  acid. 

Red  oxide  of  manganese. 

Varvicite. 


Manganic  acid. 

Of  these,  the  protoxide  may  "be  made  by  passing  hydro- 
gen gas  over  red-hot  peroxide  of  manganese.  It  is  of  a 
green  color,  is  a  basic  body,  and  forms  a  series  of  salts,  of 
which  the  sulphate  is  used  in  dyeing.  It  is  isomorphous 
with  magnesia  and  zinc.  Hydrosulphuret  of  ammonia 
yields  with  it  a  flesh-colored  precipitate,  ferrocyanide  of 
potassium  a  white,  and  the  chloride  of  soda  a  dark  brown 
hydrated  peroxide.  The  sesquioxide  is  made  by  igniting 
the  peroxide,  as  will  be  presently  explained.  The  red 
oxide  and  varvicite  occur  as  minerals ;  but  of  the  whole 
series  the  peroxide  is  by  far  the  most  valuable. 

Peroxide  of  Manganese,  Mn02=4c3'726, 
is  found  abundantly  as  a  mineral,  and  passes  in  commerce 
under  the  name  of  black  oxide  of  manganese,  a  name  in- 
dicating its  color.  It  is  insoluble  in  water,  and  when  ex- 
posed to  a  red  heat  gives  off  one  fourth  of  its  oxygen, 
forming  the  sesquioxide,  as  stated  above,  the  action  being 

How  may  manganese  be  obtained?  What  are  its  properties?  How 
many  oxides  does  it  furnish  ?  How  may  manganese  be  detected  ?  What 
is  the  constitution  of  the  peroxide  ? 


COMPOUNDS  OF  MANGANESE.  275 

2(MnO,) ...  =r  ...  Mn.2O3  +  O. 

On  this  fact  is  founded  one  of  the  processes  for  obtaining 
oxygen  gas.  Heated  with  hydrochloric  acid,  it  yields 
chlorine,  as  has  been  explained.  It  was  formerly  called 
glassmakers'  soap,  from  the  circumstance  that  it  removes, 
when  added  to  melted  glass,  the  stain  of  protoxide  of 
iron,  by  turning  it  into  peroxide,  and  causes  the  glass  to 
become  colorless ;  but  if  too  great  a  proportion  of  per- 
oxide of  manganese  is  used,  the  glass  assumes  an  ame- 
thystine color. 

Peroxide  of  manganese,  when  ignited  with  caustic  pot- 
ash in  a  platina  crucible,  yields  a  substance  known  as 
Mineral  Chameleon,  which  is  of  a  green  color.  Water 
dissolves  from  it  the  Manganate  of  Potash,  which  is  of 
a  beautiful  grass  green,  the  solution  speedily  passing 
through  a  variety  of  shades  of  purples,  blues,  and  reds. 
As  yet,  manganic  acid  is  a  hypothetical  compound,  and 
has  not  been  insulated.  When  mineral  chameleon  is 
dissolved  in  hot  water,  a  red  solution  is  obtained  of  the 
Permanganate  of  Potash  ;  from  the  permanganate  of  ba- 
ryta a  crimson  solution  of  Permanganic  Acid  may  be  pro- 
cured by  the  aid  of  sulphuric  acid  ;  but  permanganic  acid 
can  not  be  obtained  in  the  solid  form. 

Among  other  compounds  of  manganese,  the  following 
may  be  named  : 

Protochloride  of  manganese  MnCl    =    63*15. 
Perchloride     «  "  Mn^Cli  =  303'19. 

Perfluoride      "  "  MmFli  =  186-46. 

The  protochloride  may  be  made  by  acting  on  the  per- 
oxide with  muriatic  acid,  evaporating  to  dryness,  and 
fusing  at  a- red  heat.  On  digesting  with  water,  the  proto- 
chloride dissolves,  and  any  impurity  of  iron  is  left  in  the 
state  of  oxide.  Then,  by  crystallizing,  the  chloride  can 
be  obtained  in  pink  crystals.  The  perchloride  is  pro- 
duced when  permanganate  of  potash,  common  salt,  and 
sulphuric  acid  are  heated.  It  is  a  dark  greenish  and 
volatile  liquid.  The  perfluoride  is  obtained  by  distilling 
sulphuric  acid,  permanganate  of  potash,  and  fluor  spar; 
it  is  a  greenish  yellow  gas. 

What  color  does  it  give  to  glass  ?  How  is  mineral  chameleon  made  ? 
What  are  its  properties  1  Can  manganic  acid  be  insulated  ?  How  may 
the  chlorides  of  manganese  be  formed  ?  What  are  the  properties  of  the 
fluoride  ? 


. 

276  IRON.  , 

SALTS  OF  THE  PROTOXIDE  OF  MANGANESE. 

Protosulphate  of  Manganese,  formed  by  dissolving  pro- 
toxide of  manganese  in  sulphuric  acid.  The  figure  of  its 
crystals  depends  on  the  temperature  at  which  they  were 
formed.  They  have  a  rose-colored  tint.  It  is  insoluble 
in  alcohol,  very  soluble  in  water,  and  is  used  by  the  dyers 
to  produce  a  fine  brown  color. 

There  is  but  one  sulphuret  of  manganese.  It  is  ob- 
tained as  a  hydrate  when  manganese  is  precipitated  by 
hydrosulphuret  of  ammonia  (MnS,  HO).  It  is  of  a  flesh- 
red  color. 

IRON.    Fe  =  28-00. 

IRON  sometimes  occurs  in  a  native  state  and  as  mete- 
oric iron,  also  as  oxide,  carbonate,  sulphuret,  &c.  It  is 
one  of  the  most  abundant  of  the  metals.  Much  of  what 
is  found  in  commerce  is  derived  from  clay  iron-stone, 
which  is  an  impure  carbonate  containing  silica,  alumina, 
magnesia,  and  other  foreign  substances.  The  native  per- 
oxide of  iron,  red  haematite ;  the  hydrated  peroxide, 
brown  haematite ;  the  black  oxide,  or  magnetic  iron  ore, 
furnish  some  of  the  finer  varieties  of  the  metal. 

From  clay  iron-stone  metallic  iron  is  procured  by  the 
action  of  carbonaceous  matter  and  lime  at  a  high  temper- 
ature. The  ore,  having  been  roasted,  is  thrown  into  the 
furnace  with  coal  and  lime.  If  the  iron  i-s  in  the  ore  as  a 
silicate,  the  lime  decomposes  it  at  those  high  temperatures, 
forming  a  slag  of  silicate  of  lime,  and  the  oxide  of  iron 
set  free  is  instantly  reduced  by  the  carbonaceous  matter ; 
the  metal  sinking  down,  protected  by  the  slag,  is  let  off 
by  opening  a  hole  in  the  bottom  of  the  furnace. 

The  substance  thus  produced  is  not  pure  iron ;  it  con- 
tains carbon  and  other 'impurities,  and  passes  under  the 
***me  of  cast  or  pig  iron.  It  is  purified  by  melting  and 
nudden  cooling,  which  converts  it  into  fine  metal ;  this 
tine  metal  is  then  melted  under  exposure  to  air,  which 
burns  off  the  carbon  as  carbonic  oxide,  and  the  mass, 
from  being  perfectly  fluid,  becomes  coherent.  It  is  now 
subjected  to  violent  mechanical  action,  such  as  hammer^ 
ing  or  rolling ;  this  forces  out  or  burns  off  the  impurities, 

What  is  the  formation  and  use  of  the  protosulphate  of  manganese  ? 
What  are  the  forms  under  which  iron  chiefly  occurs  ?  How  is  it  obtain- 
ed from  clay  iron-stone?  What  is  cast  iron?  By  what  processes  is  it 
inverted  into  wrought  iron  ? 


•    IKON.  277 

increases  its  tenacity,  and  it  becomes  the  wrought  iron  of 
commerce. 

Cast  Iron  melts  readily  at  a  bright  red  heat,  and  expands 
in  solidifying  .  on  this  depends  its  valuable  application  for 
making  castings.  Kept  under  the  surface  of  salt  water  for 
a  length  of  time,  cast  iron  becomes  converted  into  a  body 
somewhat  like  plumbago,  due,  probably,  to  the  removal 
of  the  iron  as  a  chloride  ;  the  carbon  which  is  left  behind  is 
sometimes  observed,  as  it  dries,  to  become  hot :  a  phenom- 
enon to  be  accounted  for  by  its  porous  state.  These  facts 
have  been  frequently  verified  in  the  case  of  cannon  which 
have  lain  for  years  at  the  bottom  of  the  sea.  There  are 
two  forms  of  cast  iron,  white  and  gray ;  the  former  con- 
tains about  five  per  cent,  of  carbon,  the  latter  three  or  four. 

Pure  Iron  may  be  obtained  by  decomposing  precipitated 
peroxide  of  iron  by  hydrogen  gas,  and  melting  the  result. 
The  metal  has  a  bluish  color,  is  more  ductile  than  mallea- 
ble, and  is  the  most  tenacious  of  all  bodies.  It  becomes  very 
soft  at  a  red  heat,  and  possesses  the  welding  property ;  on 
this  depends  the  art  of  forging  it.  Its  specific  gravity  is 
7*7.  It  is  one  of  the  few  magnetic  bodies,  and,  when  soft, 
its  magnetism  is  so  transient  that  it  may  gain  and  lose  that 
quality  a  thousand  times  in  a  minute.  The  melting  point 
of  iron  is  very  high.  In  the  mode  of  preparing  it  from 
cast  iron  it  does  not  undergo  the  process  of  fusion,  but  its 
particles  are  simply  welded  together.  The  fibrous  struc- 
ture which  wrought  iron  possesses  is  the  chief  cause  of  its 
great  tenacity;  a  wire  -^th  OI*  an  mc^  m  diameter  will 
bear  a  weight  of  60  pounds. 

Steel,  which  is  a  valuable  preparation  of  iron,  is  made 
by  placing  alternate  strata  of  iron  bars  and  charcoal  pow- 
der in  a  close  box  and  keeping  them  red  hot.  The  pro- 
cess is  known  by  the  name  of  cementation.  The  iron 
gains  about  1/5  per  cent,  of  carbon.  Steel  is  much  more 
fusible  than  iron,  and  becomes  excessively  hard  and  brit- 
tle by  being  brought  to  a  red  heat  and  then  suddenly 
quenched  in  cold  water.  When  allowed  to  cool  slowly,  it 
is  quite  soft,  and  various  degrees  of  elasticity  and  hard- 
ness may  be  given  to  it  by  the  process  of  tempering. 

By  placing  a  piece  of  platina  in  nitric  acid  of  a  specific 

What  are  the  properties  of  cast  iron?  What  changes  does  it  undergo 
under  water?  How  may  pure. iron  be  obtained?  What  are  its  proper« 
ties  ?  What  is  steel  ?  How  is  it  made,  and  what  are  its  properties  f 

A  A 


278  OXIDES    OF    IRON. 

gravity  of  1*34,  and  then  bringing  an  iron  wire  in  contact 
with  it  and  withdrawing  the  platina,  the  iron  assumes  a 
passive  or  allotropic  state.  It  now  exhibits  no  tendency 
to  unite  with  oxygen,  cannot  precipitate  copper  from  its 
solutions,  and  simulates  the  properties  of  platina  and  gold. 


LECTURE  LXI. 

IRON. — Oxides  of. —  Three  Oxides  and  Ferric  Acid. —  Tests 

for  Iron. — Salts  of  the  Protoxide  and  Peroxide. —  The 

Sulphurets. — NICKEL* — Its  Reduction  from  the  Oxalate. 

—  COBALT.  —  Smalt.  —  Zaffre.  —  Sympathetic  Ink.  — 

ZINC. — Distillation  of. — Salts  of  the  Protoxide.   - 

IRON  AND  OXYGEN. 

IRON  burns  with  rapidity  in  oxygen   gas,  as  may  be 
Fig.  263.    proved  by  igniting  a  piece  of  it  in  wire  coiled 
into  a  spiral  form  in  a  jar  of  that  gas  (Fig.  263), 
when  it  will  be  found  to  take  fire  and  burn  beau- 
tifully.    In  atmospheric  air,  under  favorable  cir- 
cumstances, the  combustibility  of  this  metal  may 
be  proved.     Thus,  fine  iron  filings,  sprinkled  in 
the  flame  of  a  spirit  lamp,  burn  with  scintilla- 
tions ;  exposed  to   air  and  moisture,  it  slowly 
rusts.     Iron  yields  four  oxides  : 

Protoxide  ....  FeO  =  36-013. 
Black  oxide  .  .  .  Fe3O4  =  116-052. 
Peroxide  .  .  .  .  Fe2  O3  =  80;039. 
Ferric  acid  ....  FeO3  =  52-039. 

Protoxide  of  Iron.     FeO=36'Ol 3. 

This  oxide  has  not  yet  been  insulated,  but  it  exists, 
united  with  acids,  in  an  extensive  series  of  salts,  from 
which  it  is  thrown  down  as  a  hydrate  by  alkalies,  and  is 
then  of  a  white  color,  which  darkens  as  it  passes  into  the 
state  of  peroxide.  Ferrocyanide  of  potassium  gives  a 
white  precipitate,  and  the  ferridcyanide  a  deep  blue.  Hy- 
drosulphuret  of  ammonia  gives  a  black  sulphuret  of  iron. 
Sulphureted  hydrogen  and  gallic  acid  give  no  precipitate. 

How  may  iron  be  rendered  passive  ?  How  may  the  rapid  oxydation  of 
iron  be  illustrated  ?  How  many  oxides  does  this  metal  yield  ?  What 
are  the  reactions  which  the  protoxide  furnishes  with  tests  ? 


OXIDES    OF    IROX.  279 

Black  Oxide  of  Iron.     Fe3  O,  =  116'Q52. 

This  oxide,  known  also  as  the  magnet  or  loadstone,  is 
found  as  a  mineral.  It  is  a  compound  of  the  protoxide 
and  peroxide.  The  scales  of  iron  found  in  blacksmiths' 
forges  mainly  consist  of  it.  It  may  also  be  produced  by 
decomposing  the  vapor  of  water  by  metallic  iron  in  a  red- 
hot  tube. 

Peroxide  of  Iron,  JPe.2O3=80'039, 

is  found  in  nature  as  oligist  iron,  or  as  a  hydrate.  It  may 
be  produced  artificially  as  a  hydrate  by  precipitation  from 
a  solution  of  persulphate  of  iron  by  a  caustic  or  carbona- 
ted alkali,  or  in  a  pure  state  by  igniting  green  vitriol; 
there  is  then  left  a  red  powder,  known  as  rouge,  used  for 
polishing  metals^  This  oxide  is  not  magnetic ;  it  is  the 
basis  of  a  series  of  salts  which  yield,  with  alkalies,  a  brown 
hydrated  peroxide;  with  ferrocyanide  of  potassium,  Prus- 
sian blue  ;  with  sulphocyanide  of  potassium,  a  blood-red 
solution  ;  with  tannin  a-nd  gallic  acid,  a  black.  This  last 
is  of  considerable  interest,  constituting  the  basis  of  ordi- 
nary ink. 

The  presence  of  iron  can  always  be  determined  by 
passing  it  into  the  condition  of  peroxide,  and  applying  the 
foregoing  tests. 

Ferric  Acid,  FeO3  =  52'Q39, 

is  prepared  by  heating  peroxide  of  iron  with  four  parts  of 
nitrate  of  potash.  The  result  is  treated  with  cold  water, 
which  yields  a  red  solution  of  the  ferrate  of  potash.  This 
slowly  decomposes  in  the  cold,  and  very  rapidly  when  the 
solution  is  warm.  The  ferrate  of  baryta  precipitates 
when  the  potash  solution  is  acted  on  by  a  soluble  salt  of 
baryta.  It  is  a  permanent  body,  of  a  crimson  color. 

Among  other  compounds  of  iron,  the  following  may  bo 
named : 

Protochloride  of  iron Fed     —    63'47. 

Perchloride  "  Fe2Cl3  — 162-35. 

Protiodide  "  Fel       =  153-57. 

Protosulphnret     "  FeS       —    44-12. 

Sesquisulphuret   "  Fc*S3   =104-36. 

Bisulphuret          "  .    .     ;     t   ,.     .  Fe~S2     =    60-24. 


Under  what  natural  forms  does  the  black  oxide  occur?  How  may  it  be 
formed  artificially  ?  What  are  the  natural  forms  of  the  peroxide  ?  How 
may  it  be  prepared  1  For  what  purposes  is  it  used  ?  What  is  its  action 
with  reagents  ?  What  is  common  ink?  How  may  the  presence  of  iron 
be  detected  ?  What  are  the  properties  of  feYric  acid  ?  Of  the  other  com- 
pounds, mention  some  of  interest. 


280  SALTS    OF    IKON. 

Of  these,  the  protochloride  is  formed  by  passing  hydro- 
chloric acid  over  red-hot  iron.  It  is  white,  but  forms  a 
green  solution  in  water.  The  perchloride,  in  solution,  by 
dissolving*  peroxide  of  iron  in  hydrochloric  acid.  The 
protiodide,  by  boiling  an  excess  of  iron  filings  with  i§dine, 
and  evaporating ;  it  forms,  on  cooling,  a  dark  gray  mass. 
Its  solution  absorbs  oxygen  from  the  air.  The  protosul- 
phuret  of  iron,  which  is  much  used  for  forming  sulphuret- 
ed  hydrogen,  may  be  made  by  heating  a  mass  of  iron  to 
a  white  heat,  and  applying  to  it  roll  sulphur,  and  receiv- 
ing the  melted  globules  in  a  bucket  of  water.  It  may 
also  be  procured  by  igniting  iron  filings  with  sulphur. 
The  bisulphuret  occurs  abundantly  as  a  mineral  of  a  gold- 
en yellow  color,  crystallized  in  cubes  or  allied  forms,  and 
known  as  Iron  Pyrites.  It  frequently  assumes  the  form  of 
various  organic  remains,  being  one  of  the  common  petri- 
fying agents,  but  in  this  state  differs  essentially  from  the 
cubic  pyrites,  both  in  color  and  oxydizability,  these  fossil 
remains  rapidly  decaying  under  exposure  to  the  air,  but 
the  other  form  being  unacted  on.  Besides  these,  there  is 
a^ulphuret  of  iron  which  is  magnetic. 

SALTS  OF  THE  PROTOXIDE  OF  IRON. 

Carbonate  of  Iron  may  be  obtained  from  the  sulphate 

by  an  alkaline  carbonate,  falling  as  a  whitish  precipitate. 

'  It  turns  brown,  however,  from  the  absorption  of  oxygen. 

It  occurs  as  a  mineral  in  spathic  iron,  and  dissolves  in 

water  containing  carbonic  acid,  forming  chalybeate  waters. 

Protosulphate  of  Iron — Copperas — Green  Vitriol — is 
prepared  largely  by  the  oxydation  of  iron  pyrites,  and 
crystallizes  in  oblique  prisms  of  a  grass  green  color.  It 
has  a  styptic  taste,  dissolves  in  twice  its  weight  of  cold, 
and  three  fourths  its  weight  of  boiling  water.  It  contains 
five  atoms  of  water.  At  a  low  red  heat  it  becomes  anhy- 
drous. In  this  state  it  is  used  for  the  manufacture  of  the 
Nordhausen  sulphuric  acid. 

SALTS  OF  THE  PEROXIDE  OF  IRON. 
Persulphate  of  Iron  may  be  formed  by  adding  to  a  so 
lution  of  the  protosulphate  of  iron  half  an  equivalent  of 
sulphuric  acid,  and  peroxydizing  by  nitric  acid.     With 
water  it  forms  a  red  solution. 

What  is  iron  pyrites  ?  What  is  the  difference  of  its  forms  ?  How  is 
the  carbonate  of  iron  formed  ?  «  What  is  the  process  for  preparing  the  sul- 
phate ?  How  is  the  persulphate  obtained  ? 


NICKEL    AND    COBALT.  281 

NICKEL.     ATi  =  29'5. 

NICKEL  may  be  obtained  by  igniting  its  oxalate  in  a  cov- 
ered crucible,  carbonic  acid  escaping,  and  the  metal  being 
reduced. 

NiO+C2O3  ...=...  Ni+2(COJ ; 
one  atom  of  the  oxalate  of  nickel  yielding  one  of  the  met- 
al arid  two  of  carbonic  acid  gas. 

Nickel  is  a  white  metal,  requiring  a  high  temperatura 
for  fusion.  It  is  magnetic,  and  has  a  specific  gravity  of 
8'5.  .It  is  c6mmonly  associated  with. iron  in  meteorites, 
and  enters  into  the  composition  of  German  silver ;  unites 
with  oxygen,  forming  a  protoxide  and  sesquioxide,  the 
former  yielding  salts  of  a  green  color;  the  latter  is  an  in 
different  body. 

SALTS  OF  THE  PROTOXIDE  OF  NICKEL. 

Sulphate  of  Nickel  crystallizes  from  its  solutions  witk 
six  atoms  of  water  in  slender  green  prisms,  which,  when 
exposed  to  the  sun,  change  into  an  aggregate  of  octahe 
drons,  becoming  opaque. 

Nickel  is  chiefly  used  in  the  preparation  of  German 
silver,  an  alloy  of  copper,  zinc,  and  nickel.  It  is  of  a 
white  color,  takes  a  good  polish,  and  is  malleable. 

COBALT,  Co  =  29-5, 

is  generally  associated  with  iron  and  nickel,  and  with 
them  occurs  in  meteoric  iron.  Like  the  preceding  metal, 
it  may  be  obtained  by  igniting  its  oxalate  in  a  covered 
crucible,  carbonic  acid  being  disengaged  and  metallic 
cobalt  left.  It  is  a  pinkish  white  metal,  requiring  a  high 
temperature  for  fusion.  Its  specific  gravity  is  7*8.  ll  is 
magnetic,  as  recent  experiments  have  proved.  It  forms 
a  protoxide  and  a  sesquioxide,  the  former  being  the  basis 
of  a  class  of  salts  which  are  chiefly  of  a  pink  or  blue  col- 
or. 'Smalt  is  a  silicate  of  cobalt,  and  Zaffre  an  impure 
oxide  ;  the  former  is  used  to  communicate  to  paper  a  faint 
blue  tinge,  and  the  blue  color  which  the  oxide  gives  to 
glass  is  taken  advantage  of  in  coloring  the  common  vari- 
eties of  earthen- ware.  Cobalt  is  easily  detected  upon  this 
principle. 

By  what  process  is  nickel  obtained  ?  What  are  its  properties  ?  Under 
what  remarkable  circumstances  does  it  occur  with  iron?  What  change 
does  the  sulphate  of  nickel  undergo  in  the  sunlight?  How  is  cobalt  pro- 
cured? Is  it  magnetic  like  nickel ?  What  is  smalt?  What  is  zaffre  t 
What  are  the  uses  of  cobalt  ? 

A  A2 


282  ZINC. 

The  chloride  of  cobalt  may  be  made  by  dissolving  the 
oxide  or  the  metal  in  hydrochloric  acid.  It  is  a  pink 
solution,  which  turns  blue  when  dried.  It  forms  a  beau- 
tiful sympathetic  ink,  for  letters  written  with  it,  especially 
on  paper  which  has  a  pinkish  tinge,  are  entirely  invisible, 
but  become  of  a  bright  blue  color  when  the  paper  is 
warmed,  the  letters  again  fading  as  they  become  cool  and 
moist. 

ZINC.     Zn  =  32-3. 

ZINC  is  a  very  abundant  metal,  immense  quantities  of 
it  occurring  in  the  state  of  New  Jersey  and  in  various 
Fig.  264.     other  places.    From  zinc  blende,  which  is  a  sul- 
phuret,  converted  by  roasting  into  an  oxide,  or 
from  the  carbonate  brought  into  the  same  state 
by  ignition,  the  metal  may  be  obtained  by  the 
process   of  distillation  by  descent.     The    ox- 
ide, mixed  with  charcoal,  is  introduced  into  a 
crucible  which  has  an  iron  tube  passing  through 
a  hole  in  its  bottom,  as  seen  in  Fig.  264,  and 
the  lid  being  luted  on,  the  temperature  is  raised 
to  a  white  heat,  and  the  zinc,  distilling  over, 
may  be  condensed  in  water. 

Zinc  is  a  bluish- white  metal,  which  melts  at  about  770° 
F.,  and,  if  exposed  at  a  bright  red  heat  to  the  air,  takes 
fire  and  burns  with  a  brilliant  pale  green  flame.  Its  spe- 
cific gravity  is  about  7-00.  At  common  temperatures  it  is 
brittle,  but  it  may  be  rolled  into  thin  sheets  at  about  300° 
F.,  and  then  retains  its  malleability  when  cold.  During 
its  combustion  there  arises  from  it  a  great  quantity  of 
flocculent  oxide,  which  formerly  went  under  the  name 
of  nihil  album,  or  philosopher's  wool.  Among  the  com- 
pounds of  zinc  may  be  mentioned 

Protoxide  of  zinc ZnO  =  40-313. 

Chloride  "        ZnCl  =  67'75. 

Sulphuret        "        ZnS  ==  48'4. 

Of  these,  the  oxide  is  formed,  as  has  been  said,  during 
the  combustion  of  zinc.  It  is  also  precipitated  as  a  white 
hydrate  from  its  soluble  salts  by  potash  or  soda,  soluble 
in  excess  of  the  precipitant.  The  chloride  may  be  made 
by  the  action  of  hydrochloric  acid  on  metallic  zinc.  It  is 

What  property  does  the  chloride  possess  ?  By  what  process  is  zinc  ob- 
tained ?  Is  there  any  connection  between  its  ductility  and  temperature  ? 
During  combustion,  what  arises  from  it?  How  may  it  be  detected? 


CADMIUM. TIN.  283 

used  in  the  arts  for  soldering  under  the  name  of  butter  of 
zinc.  The  sulphuret  occurs  as  a  mineral  under  the  name 
of  zinc  blende. 

SALTS  OF  THE  PROTOXIDE  OF  ZINC. 

Sulphate  of  Zinc —  White  Vitriol. — This  salt  is  formed 
in  the  process  for  procuring  hydrogen-  gas  by  the  action 
of  dilute  sulphuric  acid  on  zinc.  It  crystallizes  in  color- 
less prisms  with  six  atoms  of  water,  and  is  soluble  in  two 
and  a  half  parts  of  cold  water.  It  has  a  styptic  taste, 
and  reddens  vegetable  blues.  There  are  three  different 
subsulphates  of  this  oxide. 

Silicate  Of  Zinc,  the  electric  calamine  of  mineralogists ; 
remarkable  for  becoming  electric  when  heated. 


LECTURE  LXII. 

CADMIUM. — Sources  of. — Its  Volatility. — TIN. — Block  and 
Grain. — Its  Properties. — Protoxide  and  Stannic  Acid. — 
Chlorides  of  Tin. — Mosaic  Gold.  —  Its  Uses. — CHRO- 
MIUM. —  Chromiron.  —  Green  Oxide  and  its  Uses.  — 
Chromic  Acid.  —  Salts  of  the  Scsquioxide. — Salts  of 
Chromic  Acid. — Other  Metals. — TITANIUM. 

CADMIUM.     Gd  =  55-8.' 

CADMIUM  usually  occurs  associated  with  zinc  as  a  car- 
bonate. In  the  preparation  of  that  metal  by  distillation, 
as  has  been  described,  the  cadmium  first  comes  over. 
From  any  impurity  of  zinc  it  may  be  separated  by  pre- 
cipitation from  an  acid  solution  by  sulphureted  hydrogen, 
which  throws  the  cadmium  down  as  a  yellow  powder, 
out  does  not  act  on  the  zinc.  The  sulphuret  of  cadmium 
is  then  dissolved  in  nitric  acid,  the  oxide  precipitated  by 
potash,  and,  when  dry,  reduced  by  charcoal.  The  com- 
pounds of  cadmium  are  not  important.  The  metal  itself 
is  very  volatile. 

TIN.     Sn  =  57-9. 

TIN  occurs  as  an  oxide  in  England,  Mexico,  Germany, 
and  the  East  Indies.  It  may  be  reduced  by  the  action 
of  charcoal  at  a  high  temperature.  It  is  found  in  corn- 
How  is  white  vitriol  prepared  ?  What  is  electric  calamine  ?  Under 
what  circumstances  does  cadmium  occur?  What  are  the  native  forms  of 
tin? 


284  COMPOUNDS    OF    TIN. 

merce  under  two  forms,  block  tin  and  grain  tin.  If  a  bar 
of  tin  is  heated,  the  purer  parts,  being  the  more  fusible, 
ooze  out  of  it,  constituting  grain  tin,  and  the  mass  which 
is  left  behind  is  block  tin. 

Tin  is  a  white  metal  like  silver.  It  oxydizes  in  the  air 
superficially,  the  action  ceasing  as  soon  as  a  thin  crust  is 
formed.  At  a  red  heat  it  oxydizes  rapidly,  forming  putty 
powder,  used  for  polishing  metals.  It  is  very  malleable, 
and  may  be  rolled  into  thin  foil.  When  bent  backward 
and  forward  it  emits  a  crackling  sound.  It  is  very  soft  ; 
its  specific  gravity  7*2.  It  melts  at  442°,  and  burns  when 
raised  to  a  high  temperature  in  the  air.  Some_of  its  com- 
pounds are 

Protoxide  of  tin    ......  SnO     =   65-913. 

Sesquioxide      .......  Sn.2O3  =  129-839 


Peroxide      ........  SnOt  =   73'926. 

Protochloride   .......  SnCL  =   93*37. 

Perchloride       .     .     .....  SnCl2  =126.74. 

Protosulphuret      ......  SnS  =    74' 

Persulphuret    .......  SnSa  =   90'1. 

The  protoxide  may  be  made  by  precipitation  from  the 
protochloride  by  carbonate  of  potash.  It  is  to  be  washed 
with  warm  water,  and  its  water  finally  driven  off  in  a  cur- 
rent of  carbonic  acid  gas  at  a  red  heat.  It  is  of  a  black 
color,  is  easily  set  on  fire  in  atmospheric  air,  passing  into 
the  condition  of  peroxide.  Its  salts  reduce  the  noble 
metals  to  the  metallic  state,  when  added  to  their  solutions, 
and  yield  with  the  chloride  of  gold  the  Purple  ofCassius. 
The  peroxide,  called  also  stannic  acid,  from  exhibiting 
weak  acid  properties,  may  be  made  by  the  action  of  ni- 
tric acid  on  tin.  It  is  a  hydrate  in  the  form  of  a  white 
powder,  insoluble  in  acids  and  water  ;  but  if  obtained  by 
precipitation  from  perchloride  of  tin,  it  is  soluble  both  in 
acids  and  alkalies.  Melted  with  glass,  it  forms  a  white 
enamel. 

The  protochloride  may  be  made  by  dissolving  tin  in 
warm  hydrochloric  acid.  The  solution,  when  concentra- 
ted, deposits  crystals  of  the  hydrated  protochloride.  These 
are  decomposed  when  heated.  The  anhydrous  protochlo- 
ride may  be  had  by  passing  hydrochloric  acid  gas  over 
metallic  tin  at  a  red  heat.  The  perchloride  is  procured 

What  are  block  and  grain  tin  ?  What  are  the  properties  of  tin  ?  When 
a  bar  of  tin  is  bent  backward  and  forward,  what  phenomenon  arises  ? 
How  is  the  protoxide  made,  and  how  do  its  salts  act  on  those  of  the  noble 
metals  ?  How  is  stannic  acid  prepared  ?  What  doea  it  yield  with  glass  ? 


CHROMIUM.  285 

by  distilling  eight  parts  of  tin  with  twenty-four  of  corro- 
sive sublimate.  It  is  a  smoking  fluid,  and  was  formerly 
called  the  Fuming  Liquor  of  Libavius*  A  solution  of 
this  substance,  much  used  in  dyeing,  is  made  by  dissolving 
tin  in  nitromuriatic  acid,  or  by  warming  a  solution  of  the 
protochloride  with  a  little  nitric  acid. 

Of  the  sulphurets,  the  first  may  be  formed  by  pouring 
melted  tin  on  sulphur,  and  igniting  the  powdered  result 
with  more  sulphur  in  a  crucible.  It  is  a*bluish  gray  com- 
pound. The  persulphuret  is  obtained  when  two  parts  of 
peroxide  of  tin,  two  of  snlphur,  and  one  of  sal  ammoniac 
are  ignited  in  a  retort.  It  is  a  body  of  a  golden  yellow 
color,  formerly  called  Aurum  Musivum,  or  Mosaic  gold, 
in  small  scales  of  a  greasy  feel,  and  is  used  for  exciting 
electrical  machines,  being  much  more  energetic  than  the 
common  amalgam,  though  less  durable  in  its  power. 

Tin  furnishes  several  valuable  metallic  combinations  ; 
Tin  Plate  is  sheet  iron  superficially  alloyed  with  it. 
The  soft  solders  are  alloys  of  lead  and  tin.  Pewter  is  an 
alloy  with  antimony. 

CHROMIUM.     Cr=28. 

CHROMIUM  occurs  abundantly  near  Baltimore  as  the 
chromate  of  iron  (Chrome  Iron), more  rarely  as  the  red  chro- 
mate  of  lead.  The  metal  may  be  obtained  by  the  action 
of  charcoal  on  the  oxide  at  a  high  temperature,  and  is  of 
a  yellowish-white  color.  It  takes  its  name  from  its  tend- 
ency to  produce  highly  colored  compounds.  It  is  very 
infusible,  and  has  a  specific  gravity  of  about  G'OO.  Its  com- 
pounds, to  be  here,  described,  are 

Sesqaioxide  of  chromium    .     .     .     .  Cr2O3=    80'039. 

Chromic  acid CrO3    =    52-039. 

Sesquichloride  of  chromium     .     .     .  Cr2Cl3  =  162-26. 

The  sesquioxide  may  be  prepared  by  heating  the  chro- 
mate of  mercury  to  redness  in  a  crucible.  The  mercury 
is  driven  off,  and  the  chromic  acid  partially  deoxydized, 
leaving  a  beautiful  grass-green  powder,  the  sesquioxide. 
It  may  also  be  obtained  by  heating  the  bichromate  of  pot- 
ash red  hot,  and  washing  the  residue  in  water ;  also  as  & 
hydrate,  by  boiling  a  solution  of  bichromate  of  potash  with 

What  is  the  fuming  liquor  of  Libavius  ?  How  is  mosaic  gold  made, 
and  what  is  its  use  ?  What  alloys  does  tin  furnish  ?  Under  what  forms 
does  chromium  occur  in  nature  ?  How  is  its  sesquioxide  prepared,  and 
what  is  its  use  ? 


286  COMPOUNDS  OF  CHROMIUM. 

muriatic  acid,  and  adding  alcohol ;  the  mixture  becomes 
of  a  green  color,  and  ammonia  precipitates  the  hydrated 
sesquioxide.  It  is  a  weak  base,  yielding  a  class  of  salts 
of  a  blue  or  green  color.  In  the  state  of  hydrate  it  is  sol- 
uble in  acids  ;  but,  on  making  it  red  hot,  it  suddenly  be- 
comes incandescent,  passes  into  another  allotropic  state, 
and  is  now  insoluble.  This  sesquioxide  is  isomorphous 
with  the  sesquioxides  of  iron  and  alumina.  In  its  two  al- 
lotropic states,  it  yields  corresponding  classes  of  salts,  one 
of  which  is  green,  and  the  other  reddish  green.  It  is  used 
for  communicating  a  green  color  to  porcelain. 

Chromic  Acid  may  be  made  by  adding  one  volume  of  a 
saturated  solution  of  bichromate  of  potash  to  one  and  a 
half  of  oil  of  vitriol.  On  cooling,  red  crystals  of  chromic 
acid  are  deposited.  It  is  isomorphous  with  sulphuric  acid, 
produces  with  bases  yellow  and  red  ;salts,  is  a  powerful 
oxydi-zing  agent,  is  decomposed  by  a  red  heat  into  the  ses- 
quioxide, destroys  the  color  of  indigo  and  other  dyes, 
and  may  be  detected  by  producing  with  the  salts  of  lead, 
chrome  yellow,  and  by  its  ready  passage,  under  the  influ- 
ence of  deoxydizing  agents,  into  the  sesquioxide. 

The  sesquichloride  is  procured  when  chlorine  is  passed 
over  a  mixture  of  the  sesquioxide  and  charcoal  in  a  red- 
hot  tube.  It  is  a  lilac-colored  body,  which  forms  a  green 
solution  in  water.  There  is  also  an  oxy chloride,  which 
may  be  distilled  as  a  deep-red  liquid  from  a  mixture  of 
chromate  of  potash,  common  salt,  and  oil  of  vitriol.  The 
fluoride,  which  is  a  red  gas,  is  obtained  by  distilling  in  a 
silver  retort  a  mixture  of  chromate  of  lead,  fhior  spar,  and 
oil  of  vitriol.  It  is  decomposed  by  the  moisture  of  the  air, 
forming  chromic  and  hydrofluoric  acids. 

SALTS  OF  THE"  SESdUIOXIDE  OF  CHROMIUM. 
Sulphate  of  Chromium  and  Potash — Chrome  Alum. — 
When  the  oxide  of  chromium  is  dissolved  in  sulphuric 
acid  and  mixed  with  the  sulphate  of  potash  and  a  little 
free  sulphuric  acid,  crystals  of  chrome  alum  are  deposit- 
ed in  red  or  blue  octahedrons.  The  sulphate  of  chromium 
alone  does  not  crystallize. 

Chrome  Iron,  a  compound  of  the  sesquioxide  of  chro- 
mium and  the  protoxide  of  iron,  is  found  native,  crystal- 
How  is  chromic  acid  made  ?     Does  it  possess  bleaching  powers  ?     How 
are  the  chloride  and  fluoride  obtained  ?     What  is  the  form  of  the  latter 
body  ?     What  is  chrome  alum  ? 


SALTS  QF  CHROMIC  ACID.  287 

lized  in  octahedrons,  and  also  massive.     It  furnishes  most 
of  the  compounds  of  chromium. 

SALTS  OF  CHROMIC  ACID. 

Chromate  of  Potash  may  be  made  by  igniting  chrome  iron 
with  one  fifth  its  weight  of  nitrate  of  potash.  It  crystal- 
lizes in  small,  lemon-yellow  prisms,  and  is  very  soluble 
in  hot  water.  The  crystals  are  anhydrous. 

Bichromate  of  Potash  may  be  prepared  from  the  for- 
mer by  adding  an  equivalent  of  acetic  acid :  it  crystal- 
lizes in  prisms  of  a  ruby  red.  Large  quantities  are  con- 
sumed by  dyers. 

Chromate  of  Lead- — Chrome  Yellow,  obtained  by  pre- 
cipitation from  either  of  the  foregoing  salts  by  a  soluble 
salt  of  lead.  It  is  used  as  a  paint. 

Dichromate  of  Lead  is  formed  by  adding  chromate  of 
lead  to  melted  nitrate  of  potash,  arid  dissolving  out  the 
chromate  of  potash  and  excess  of  nitre  by  water.  It  is  of 
a  beautiful  red  color. 

The  following  metals,  VANADIUM,  TUNGSTEN,  MOLYB- 
DENUM, OSMIUM,  and  COLUMBIUM,  are  not  applied  to  any 
purposes  in  the  arts,  or  are  so  rare  as  not  to  be  of  general 
interest.  TITANIUM  might  be  included  in  the  same  obser- 
vation ;  it  is,  however,  deserving  of  remark  as  being  a  red 
metal  like  copper,  and  titanic  acid,  one  of  its  oxygen  com- 
pounds, is  used  in  the  coloring  of  artificial  teeth. 


LECTURE  LXIII. 

ARSENIC. — Preparation  of  the  Metal. — Properties  of  Ar- 
senious  Acid. —  Two  Varieties  of  it. —  Two  methods  of 
detecting  it. — Process  in  Cases  of  Poisoning, — Sulphur- 
eted  Hydrogen  Test. — Marsh's  Test. —  The  Copper  Test. 
— Difficulties  arising  from  Antimony^ 

AUSENIC.     As  —  37-7. 

ARSENIC  is  obtained  by  sublimation  in  a  current  of  air 
of  the  arseni'uret  of  cobalt  and  iron,  the  vapor  condensing 
as  a  white  oxide.  This  being  mixed  with  powdered  char- 

What  is  the  constitution  of  the  two  chromates  of  potash  ?  What  is 
chrome  yellow  ?  "What  is  the  color  of  titanium  ?  From  what  substances, 
and  in'  what  manner,  is  arsenious  acid  prepared  ? 


288  COMPOUNDS    OF    ARSENIC. 

Fig.  265  coal,,  or  black  flux,  and  heated,  the  metallic  arse- 
nic sublimes.  The  process  may  be  conducted  in 
a  tall  vial  imbedded  in  a  crucible  filled  with  sand, 
two  thirds  of  the  vial  projecting  above  the  heated 
sand.  On  this  cooler  portion  the  metal  condenses. 
It  is  also  sometimes  found  in  a  native  state. 
Arsenic  is  a  metallic  body,  of  an  aspect  darker  than  cast 
iron  ;  it  is  very  brittle,  its  specific  gravity  is  5*88,  and,  when 
slowly  sublimed,  it  crystallizes  in  rhombohedrons.  At 
356°  F.  it  sublimes  without  undergoing  fusion,  its  melting 
point  being  much  higher  than  that  of  sublimation.  Its  va- 
por has  a  smell  of  garlic,  as  may  be  readily  recognized  by 
throwing  a  little  arsenious  acid  on  a  red-hot  coal.  Arse- 
nic prepared  by  black  flux  tarnishes,  it  is  said,  from  con- 
taining a  little  potassium.  Among  its  compounds,  the  fol- 
lowing may  be  mentioned : 

Arsenious  acid      ^    .....     .  As^O3^=   99-439. 

Arsenic  acid As2O5  =  115-465. 

Protosulphuret  of  arsenic  .  .  .  .  AsS  =  53-8. 
Sesquisulphuret  of  arsenic  .  .  .  As2S3  =  123-7. 
Arseniureted  hydrogen  ....  AsH  =  38'7. 

Arsenious  Acid  is  formed  when  arsenic  is  sublimed  in 
atmospheric  air.  It  is  a  white  substance,  which,  when 
the  process  is  conducted  slowly,  crystallizes  in  octahe- 
drons. Similar  octahedral  crystals  may  be  obtained  by 
heating  arsenious  acid  itself  in  a  tube  to  380°  F.  When 
the  operation  has  been  recently  performed  and  a  large 
mass  sublimed,  it  is  a  glassy,  transparent  body,  which  in 
the  course  of  time  slowly  becomes  milk-white.  The  spe- 
cific gravity  of  arsenious  acid  is  3'7.  It  is  nearly  taste- 
less, of  sparing  solubility  in  water,  the  two  varieties  dif- 
fering in  this  respect.  By  100  parts  of  water,  11*5  of  the 
opaque,  but  only  9'7  of  the  transparent,  are  dissolved. 
This  substance  passes  currently  under  the  name  of  arse- 
nic. It  ought  not  to  be  forgotten  that  the  arsenic  of  chem- 
ical writers  and  that  of  commerce  are  very  different  bod- 
ies :  the  one  is  black  and  the  other  white ;  the  one  is  a 
metal  and  the  other  its  oxide. 

Arsenious  acid  may  be  detected  by  several  methods. 

How  is  the  metal  ohtained  from  it  ?  What  are  its  properties  ?  What 
is  the  odor  of  its  vapor  ?  Why  can  not  it  be  melted  ?  From  the  metal, 
MOW  may  arsenious  acid  he  procured  ?  What  change  does  the  glassy  va- 
riety undergo  in  time  ?  Of  these  varieties,  which  is  most  soluble  in  water  ? 
What  is  the  difference  between  the  arsenic  of  chemists  and  the  arsenic 
of  commerce  ? 


TESTS    FOR    ARSENIC.  289 

1st.  "With  ammonia  sulphate  of  copper,  it  gives  an 
emerald  green  precipitate  ;  the  arsenite  of  copper,  or 
Scheele's  green. 

2d.  With  the  ammonia  nitrate  of  silver,  a  canary  yel- 
low precipitate  ;  the  arsenite  of  silver. 

3d.  With  sulphureted  hydrogen,  a  solution,  previously 
acidulated  with  acetic  or  muriatic  acid,  yields  a  yellow  pre- 
cipitate, the  sesquisulphuret  of  arsenic,  orpiment.  This, 
when  dried  and  ignited  with  black  flux  (a  mixture  of 
charcoal  and  carbonate  of  potash,  obtained  by  igniting 
cream  of  tartar  in  a  covered  crucible),  yields  a  sublimate 
of  metallic  arsenic. 

4th.  With  the  materials  for  generating  hydrogen  gas ; 
that  is,  sulphuric  acid,  zinc,  and  water*,  placed  in  a  bottle ; 
if  arsenious  acid  be  present,  arseniureted  hydrogen  is  dis- 
engaged. When  set  on  fire,  it  burns  with  a  pale  blue 
flame,  emitting  a  white  smoke  ;  and  if  a  piece  of  cold  glass 
be  held  in  the  flame,  there  is  deposited  upon  it  a  black 
spot  of  arsenic,  surrounded  by  a  white  border  of  arsen- 
ious acid.  This  stain  is  volatilized  on  heating  the  glass. 
Or  if  the  arseniureted  hydrogen  be  conducted  through  a 
tube  of  Bohemian  glass,  made  red  hot  at  one  point  by  a 
spirit  lamp,  it  is  decomposed,  and  metallic  arsenic  depos- 
ited on  the  cooler  portions  beyond  the  ignited  space. 

5th.  If  a  solution  containing  arsenious  acid  be  acidu- 
lated with  hydrochloric  acid,  and  boiled  with  slips  of  cop- 
per, the  metallic  arsenic  is  deposited  upon  the  copper  vis 
an  iron  gray  crust. 

In  cases  of  poisoning  by  this  substance,  it  is  unsatisfac- 
tory to  apply,  in  the  first  instance,  color-giving  tests,  such 
as  the  first,  second,  and  third ;  as  the  liquid  obtained  from 
the  stomach  is  itself  highly  colored  and  turbid.  It  is, 
therefore,  desirable  to  examine  that  organ  and  its  contents 
minutely,  endeavoring  to  discover  any  white  granules,  or 
specks,  which  may  be  supposed  to  be  arsenious  acid,  and 
if  such  are  found,  to  examine  them  separately. 

The  contents  of  the  stomach,  the  larger  pieces  having 
been  divided,  are  to  be  boiled  in  water,  and  strained 
through  a  linen  cloth.  A  current  of  chlorine  gas  passed 

What  is  the  action  of  ammonia  sulphate  of  copper  on  arsenious  acid  ? 
What  of  the  ammonia  nitrate  of  silver  ?  What  of  sulphureted  hydrogen  ? 
What  is  the  process  for  detecting  it  by  arseniureted  hydrogen  ?  What  is 
that  by  copper  ?  In  cases  of  poisoning,  why  can  not  color  tests  be  applied  1 
How  is  the  liquid  obtained  from  the  stomach  to  be  clarified  ! 

BB 


290 

through  this  liquid  coagulates  and  separates  much  of  the 
animal  matter ;  or,  what  is  more  convenient,  if  the  solu- 
tion be  first  acidulated  with  nitric  acid,  and  then  nitrate 
of  silver  be  added,  much  of  the  animal  matter  may  be  re- 
moved. By  the  addition  of  a  solution  of  common  salt,  the 
excess  of  the  silver  salt  may  be  precipitated,  and  the 
liquor  being  filtered,  is  then  fit  for  the  third  or  fourth  of 
the  foregoing  tests. 

In  the  application  of  sulphureted  hydrogen,  the  liquor 
having  been  clarified  as  just  stated,  the  gas  is  passed 
through  it  until  it  smells  strongly.  It  is  then  to  be  boiled 
for  a  short  time,  to  expel  the  excess  of  gas,  and  filtered. 
The  yellow  precipitate  of  sesquisulphuret  of  arsenic,  or 
orpiment,  which  is*  collected,  is  to  be  thoroughly  dried, 
and  introduced,  with  twice  its  bulk  of  black  flux,  into  the 
Fig.  266.  bulb,  «,  of  a  tube,  such  as  Fig.  266,  made  of 
hard  glass.  On  the  temperature  being  rais- 
ed by  a  lamp,  metallic  arsenic  sublimes, 
forming  an  iron  black  ring  round  the  part, 
b.  By  cutting  off  the  bulb  of  the  tube  and 
heating  the  black  crust  gradually,  it  slowly  sublimes  to- 
ward the  colder  part,  producing  a  white  deposit  of  ar- 
senious  acid  in  octahedral  crystals. 

In  the  application  of  Marsh's  test,  the  liquor,  having 
been  cleared  either  by  chlorine  or  by  nitrate  of  silver,  as 
above  described,  is  to  be  introduced  into  a  bottle  con- 
taining dilute  sulphuric  acid  and  zinc,  a  tube,  bent  as 
Fig.  267.  represented  in  Fig.  267,  tz,  passing  lat- 

erally  from  the  cork;  arseniureted  hy- 
drogen now  passes  off,  and  may  be  set 
on  fire  as  it  escapes  from  the  end  of  the 
tube,  and  examined  by  holding  in  the 
flame  a  piece  of  cold  glass,  b.  If  no  spot 
be  produced,  then  the  tube,  which  for  this  reason  should 
be  made  of  a  hard  glass  not  containing  lead,  is  to  be  ignit- 
ed by  a  spirit  lamp  at  the  point  c,  and  the  gas  will  de- 
posit its  arsenic  a  little  beyond  that  point.  In  this  mari- 
ner, the  tube  being  kept  red  hot  for  hours,  the  smallest 
quantity  of  arsenic  may  be  discovered. 

If  the  liquor,  notwithstanding  the  care  taken  to  clear  it, 

Describe  the  test  by  sulphureted  hydrogen.  Describe  Marsh's  test. 
How  may  a  small  quantity  of  metal  be  separated  from  a  large  quantity  of 
liquid  by  this  test  ? 


ARSENIC.  291 

froths  when  the  hydrogen  is  disengaged,  so  as  to  inter- 
fere with  the  results  by  choking  the  tube,  the  gas  is  best 
collected  under  a  jar  at  the  pneumatic  trough,  and  may  be 
subsequently  examined. 

The  fifth  test,  by  copper,  may  be  sometimes  advanta- 
geously applied  to  collect  the  arsenic  from  solutions ;  the 
crust  upon  the  copper  may  be  subsequently  examined,  ei- 
ther by  sublimation  or  otherwise. 

It  is  to  be  remembered  that  antimony  will  yield  results 
closely  resembling  those  of  arsenic  by  Marsh's  test ;  but 
on  heating  the  glass  plate  on  which  the  stain  has  been  de- 
posited, if  it  be  arsenic,  it  will  totally  volatilize  away;  but, 
if  antimony,  though  the  flame  of  a  blow-pipe  be  thrown 
upon  it,  it  will  not  disappear,  but  only  gives  rise  to  a  yel- 
low oxide,  which  turns  white  on  cooling. 

In  medico-legal  investigations,  it  should  also  be  re- 
membered that,  as  sulphuric  acid  and  zinc  of  commerce 
sometimes  contain  arsenic,  it  is  absolutely  necessary  that 
the  specimens  about  to  be  used  be  -critically  examined 
themselves  by  being  tried  alone  before  the  suspected  so- 
lution is  added. 


LECTURE  LXIV. 

ARSENIC. — Antiseptic  Quality  of  Arsenious  Acid. — Anti- 
dote for  Poisoning. — Arsenic  Acid. — Isomorphous  with 
Phosphoric  Acid. — Realgar  and  Orpiment. — Arseniuret- 
ed  Hydrogen. — ANTIMONY. — Reduction  of. —  Oxides, 
Chlorides,  and  Sulphurets  of. — Antimoniureted  Hydro- 
gen.— Detection  of  Antimony. — TELLURIUM. — URANIUM. 
— COPPER. — Reduction  of. —  Use  of  Oxide. — Detection 
of. — Salts  of  Protoxide. 

ARSENIOUS  ACID  possesses  a  remarkable  antiseptic  qual- 
ity, and  hence  often  preserves  the  bodies  of  persons  who 
have  been  poisoned  by  it.  Advantage  is  also  taken  of  this 
fact  by  the  collectors  of  objects  of  natural  history  in  pre- 
serving their  specimens. 

When  the  liquid  froths,  what  course  is  to  be  pursued  ?  When  may  the 
test  of  copper  be  advantageously  applied  ?  What  metal  closely  resembles 
arsenic  in  these  respects  ?  Why  is  it  necessary  to  examine  the  sulphuric 
acid  and  zino  employed  in  these  experiments  ?  Does  arsenious  acid  pos- 
sess an  antiseptic  quality  ? 


292  COMPOUNDS    OF    ARSENIC. 

The  antidote  for  poisoning  by  arsenic  is  the  hydrated 
eesquioxide  of  iron.  It  may  be  made  by  adding  carbon- 
ate of  soda  to  the  muriate  of  iron.  It  should  be  given  in 
the  moist  state,  mixed  with  water.  After  being  once 
dried,  it  loses  much  of  its  power.  It  produces  an  inert 
basic  arsenite  of  the  peroxide  of  iron. 

Arsenic  Acid  is  found  in  nature  in  union  with  various 
bases.  It  may  be  made  by  acting  on  arsenious  acid  with 
nitric  acid,  with  the  addition  of  a  little  hydrochloric  acid, 
and  evaporating  till  the  nitric  acid  is  expelled.  The  re- 
sulting acid  contains  three  atoms  of  water,  and  is  isomor- 
phous  with  tribasic  phosphoric  acid.  The  arseniates  yield, 
with  nitrate  of  silver,  a  dark-red  precipitate  of  the  triba- 
sic arseniate  of  silver.  The  monobasic  and  bibasic  forms 
of  the  acid  are  not  known.  It  should  not  be  forgotten  in 
medico-legal  inquiries  respecting  arsenic,  that  the  arse- 
niate of  lime  may  naturally  replace  phosphate  of  lime  in 
bone  earth,  and  this  acid  substitute  the  phosphoric  in  other 
parts  of  the  system. 

The  protosulphuret  of  arsenic  may  be  obtained  by  melt- 
ing arsenious  acid  with  sulphur.  It  occurs  as  a  mineral 
Realgar,  and  is  a  red-colored  substance. 

The  sesquisulphuret  is  deposited  when  a  stream  of  sul- 
phureted  hydrogen  is  passed  through  a  solution  of  arse- 
nious acid.  It  is  a  yellow  body,  and  is  used  in  dyeing ; 
it  is  also  known  under  the  name  of  Orpiment. 

Arseniureted  Hydrogen  is  prepared  by  acting  on  an  al- 
loy of  zinc  and  arsenic  with  dilute  sulphuric  acid.  It  is 
a  colorless  gas,  burns  with  a  blue  flame,  exhales  an  odor 
like  garlic.  Its  specific  gr^ity  is  2*695.  It  is  decom- 
posed by  chlorine,  iodine,  and  the  arsenic  is  separated  by 
heat  and  by  the  rays  of  the  sun. 

ANTIMONY.     Sb  =  64-6. 

This  metal  occurs  commonly  as  a  sesquisulphuret  in 
nature,  from  which  it  may  be  obtained  by  heating  with 
iron  filings,  a  sulphuret  of  iron  forming,  and  metallic  an- 
timony subsiding  to  the  bottom  of  the  crucible.  It  may 
also  be  obtained  by  fusing  the  sulphuret  with  black  flux, 

What  is  the  antidote  for  this  poison?  How  is  it  prepared?  How  is 
arsenic  acid  prepared  ?  What  fact  arises  from  the  isomorphism  of  arsen- 
ic and  phosphoric  acids  ?  What  is  realgar  ?  What  is  orpiment  ?  How 
may  arseniureted  hydrogen  be  made  ?  From  what  source  is  antimony  ob- 
tained ?  What  is  the  process  for  its  preparation  ? 


COMPOUNDS    OF    ANTIMONY.  293 

which  produces  a  sulphuret  of  potassium  and  metallic 
antimony. 

Antimony  is  a  blue-white  metal,  of  a  very  crystalline 
structure,  and  so  brittle  that  it  may  be  pulverized.  It 
melts  at  810°  F.  Its  specific  gravity  is  6'7.  It  possess- 
es, at  high  temperatures,  an  intense  affinity  for  oxygen  ;  a 
fragment  of  it  the  size  of  a  pea  being  ignited  on  a  piece 
of  charcoal  before  the  blow-pipe,  and  then  suddenly  thrown 
on  the  table,  takes  fire,  breaking  into  a  multitude  of  glob- 
ules, and  filling  the  air  with  fumes  of  the  white  sc&qui- 
oxide.  Antimony  yields  the  following  compounds : 

Sesquioxide  of  antimony     ....  Sb2  O3   =  153-239. 

Antimonious  acid &£204  =161-252. 

Antimonic  acid Sb2  Or,   =  169'265. 

Sesquichloride  of  antimony  Sb2  C13  =  235*46. 

Perchloride  "          .  £62C75 -=306'3. 


Sesquisulphuret 

Persulphuret 

Oxysulphuret 


:  177-5. 
SB  =209-7. 
tS,  +  SbaO,=: 


The  Sesquioxide  of  Antimony  may  be  made  by  adding 
to  an  acid  boiling  solution  of  chloride  of  antimony  car- 
bonate of  soda.  It  is  a  gray  powder,  and  is  the  base  of  a 
class  of  salts,  among  which  tartar-emetic  may  be  men- 
tioned. These  salts  give  an  orange-colored  precipitate 
with  sulphureted  hydrogen. 

Antimonious  Acid  is  produced  by  heating  the  oxide  of 
antimony,  or  antimonic  acid.  It  is  a  white  powder,  and 
unites  with  bases,  forming  antimonites. 

Antimonic  Acid  may  be  prepared  by  acting  on  metallic 
antimony  with  nitric  acid. 

Sesquichloride  of  Antimony  is  made  by  dissolving  one 
part  of  sulphuret  of  antimony  in  five  of  hydrochloric  acid, 
and  distilling.  As  soon  as  the  matter  which  passes  over 
becomes  solid,  the  receiver  is  to  be  changed,  and,  contin- 
uing the  heat,  the  sesquichloride  is  collected.  It  was  for- 
merly known  as  butter  of  antimony.  The  perchloride 
may  be  made  by  burning  antimony  in  chlorine  gas.  The 
oxy chloride  is  produced  when  the  sesquichloride  is  placed 
in  contact  with  water.  It  was  formerly  known  as  pow- 
der of  algaroth. 

The  sesquisulpliuret  occurs  abundantly  as  a  mineral,  as 

What  are  its  properties  ?  What  color  is  the  precipitate  yielded  by  the 
salts  of  the  sesquioxide  and  sulphureted  hydrogen  ?  How  is  antiinonious 
acid  prepared  ?  What  is  the  butter  of  antimony  ?  What  is  the  powder 
of  algaroth?  What  is  the  aspect  of  the  native  sesquisulphuret  ? 

B  B  2 


294  COMPOUNDS  OF  ANTIMONY. 

has  been  said.  It  is  also  formed  by  the  action  of  sulphu- 
reted  hydrogen  on  the  salts  of  the  oxide  of  antimony.  In 
this  case  it  is  of  an  orange  color,  in  the  former  it  has  a 
metallic  aspect.  The  persulphuret  is  procured  when  the 
sesquisulphuret  and  sulphur  are  boiled  in  a  solution  of 
potash,  the  liquor  filtered,  and  an  acid  added,  a  yellow 
precipitate  going  down.  It  was  known  formerly  as  the 
Golden  Sulphurel  of  Antimony.  The  oxysulphuret  occurs 
native  as  the  red  ore  of  antimony,  and  may  also  be  made 
by  boiling  the  sesquisulphuret  with  a  solution  of  potash. 
On  cooling,  precipitation  of  it  takes  place.  It  is  stated, 
however,  by  Berzelius,  that  this  is  not  a  true  compound, 
but  merely  a  mechanical  mixture  of  the  oxide  and  sulphu- 
ret  in  irregular  proportions.  This  precipitate  is  also  known 
under  the  name  of  Kermes  Mineral.  From  the  liquor,  af- 
ter the  kermes  is  separated,  an  acid  throws  down  the  gold- 
en sulphuret  of  antimony. 

Antimoniureted  Hydrogen. — ^When  hydrogen  is  evolved 
from  a  solution  containing  tartar  emetic  (tartrate  of  anti- 
mony and  potash),  this  substance  is  produced.  It  is  a  gas, 
having  a  superficial  resemblance  to  arseniureted  hydro- 
gen, and  when  used  as  in  Marsh's  apparatus,  gives  a  stain 
on  glass  resembling  that  of  arsenic.  From  arsenic  it  may 
be  distinguished  by  not  being  volatile. 

The  soluble  salts  of  antimony  may  be  distinguished  by 
giving  an  orange  precipitate  with  sulphureted  hydrogen, 
soluble  in  sulphuret  of  ammonium,  but  again  precipitated 
by  an  acid. 

Antimony  furnishes  some  valuable  alloys :  printer's 
type  metal,  for  example,  is  an  alloy  of  this  substance  with 
lead.  It  expands  in  the  act  of  solidifying,  and,  therefore, 
takes  accurate  impressions  of  the  interior  of  a  mould. 

TELLURIUM.     Te  =  6W. 

TELLURIUM  is  a  rare  metal,  of  a  white  color,  very  fusi- 
ble and  volatile,  having  several  analogies  with  selenium, 
and  uniting  with  hydrogen  to  form  tellureted  hydrogen, 
which,  with  water,  yields  a  claret-colored  solution. 

URANIUM,  U=  217, 
is  likewise  a  very  rare  metal,  of  the  nature  of  which  there 

What  is  the  golden  sulphuret  ?  What  is  Kermes  mineral  ?  How  is 
antimoniureted  hydrogen  made  ?  How  may  the  salts  of  antimony  be  dis- 
tinguished? What  are  the  properties  of  tellurium? 


COPPER.  295 

are  considerable  doubts,  it  being  supposed  that  what  was 
formerly  regarded  as  the  metal  is  in  reality  its  protoxide. 
It  may  be  remarked,  if  these  observations  are  incorrect, 
that  uranium  has  the  highest  equivalent  of  any  of  the  ele- 
mentary bodies.  It  is  used  to  a  small  extent  to  give  black 
and  yellow  colors  to  porcelain. 

COPPER.    Cu  =  31-6. 

COPPER  is  often  found  native,  and  in  certain  parts  of  the 
United  States  in  masses  of  very  great  magnitude.  It  also 
occurs  as  a  carbonate  and  sulphuret.  In  the  latter  com- 
bination, it  is  found  with  the  sulphuret  of  iron,  as  yellow 
copper  ore.  This  being  roasted,  the  sulphuret  of  iron 
changes  into  oxide,  the  copper  sulphuret  remaining  un- 
changed. The  mass  is  then  heated  with  sand,  which 
yields  a  silicate  of  iron,  the  sulphuret  of  copper  separa- 
ting. This  process  is  repeated  until  all  the  iron  is  parted  ; 
and  now  the  sulphuret  of  copper  begins  to  change  into 
the  oxide,  which  is  finally  decomposed  by.  carbon  at  a  high 
temperature. 

Copper  is  a  red  metal,  requiring  a  high  temperature  for 
fusion.  Its  specific  gravity  is  8-617.  It  has  great  tenac- 
ity, and  is  ductile  and  malleable.  A  polished  plate  of 
it,  heated,  exhibits  rainbow  colors,  and  is  finally  coated 
with  the  black  oxide.  It  is  one  of  the  best  conductors  of 
heat  and  electricity.  Among  its  compounds,  the  follow- 
ing may  be  mentioned : 

Protoxide  of  copper CuO    =39-613. 

Suboxide  "  Cu^O  =71-213. 

Chloride  "  CuCl   =66-02. 

Bichloride          "  C«2C7  =  98-62. 

Disulphuret        "  Cu2S  =79'32. 

Protoxide  of  Copper  may  be  made  either  by  igniting  me- 
tallic copper  in  contact  with  air,  or  by  calcining  the  ni- 
trate. It  is  a  black  substance,  not  decomposable  by  heat, 
but  yielding  oxygen  with  facility  to  carbon  and  hydrogen, 
and  hence  extensively  used  in  organic  analysis.  It  is  a 
base,  yielding  salts  of  a  blue  or  green  color.  The  sub- 
oxide,  called,  also,  red  oxide,  occurs  native  as  ruby  cop- 
per. It  is  a  feeble  base.  The  disulphuret  also  occurs 
native,  as  copper  pyrites. 

What  is  remarkable  as  respects  the  alleged  atomic  weight  of  uranium  ? 
Under  what  forms  does  copper  naturally  occur?  What  is  the  process  for 
its  reduction?  What  are  its  properties  ?  Which  of  its  oxides  is  used  in 
organic  analysis  ? 


296  SALTS    OF    COPPER. 

Copper  is  easily  detected.  Caustic  potash  gives,  with 
its  protosalt,  a  pale-blue  hydrate,  which  turns  black  on 
boiling.  Ammonia,  in  excess,  yields  a  beautiful  purple 
solution  ;  ferrocyanide  of  potassium,  a  chocolate  brown 
precipitate  ;  sulphureted  hydrogen,  a  black*;  and  metallic 
iron,  as  the  blade  of  a  knife,  precipitates  metallic  copper. 

SALTS  OF  THE  PROTOXIDE  OF  COPPER. 

Carbonate  of  Copper. — The  neutral  carbonate  of  cop- 
per is  not  known ;  but  there  are  several  varieties  of  di- 
carbonates.  One,  which  passes  under  the  name  of  Miner- 
al Green,  is  formed  by  precipitating  with  -an  alkaline  car- 
bonate. It  occurs  naturally  in  the  form  of  Malachite. 
Slue  copper  ore  is  another  dicarbonate ;  the  paint  called 
Green  Verditer  has  a  similar  composition. 

Sulphate  of  Copper — Blue  Vitriol — is  prepared  for  com- 
merce by  the  oxydation  of  the  sulphuret  of  copper.  It 
crystallizes  in  rhomboids  of  blue  color,  with  four  atoms  of 
water.  It  is  'soluble  in  four  times  its  weight  of  cold,  and 
twice  its  weight  of  hot  water.  It  is  an  escharotic,  an  as- 
tringent, and  has  an  acid  reaction.  With  ammonia  it  forms 
a  compound  of  a  splendid  blue  color,  which  may  be  ob- 
tained in  crystals ;  with  potash,  also,  it  forms  a  double 
salt.  There  are  also  subsulphates  of  copper. 

Nitrate  of  Copper,  formed  by  the  action  of  nitric  acid  on 
metallic  copper.  It  crystallizes  in  prisms,  or  in  plates. 
It  acts  with  very  great  energy  on  metallic  tin.  There  is 
a  subnitrate  of  copper. 

Arsenite  of  Copper — Scheelc's  Green — produced  by  add- 
ing solution  of  arsenious  acid  to  the  solution  of  ammonia 
sulphate  of  copper. 

Copper  yields  several  valuable  alloys.  Brass  is  an  al- 
loy of  copper  and  zinc  ;  gun  metal,  bell  metal,  and  spec- 
ulum metal,  of  copper  and  tin.  The  gold  and  silver  of 
currency  contain  portions  of  this  metal ;  it  communicates 
to  them  the  requisite  degree  of  hardness. 

How  may  copper  be  detected  ?  Under  what  forms  do  the  carbonates 
of  copper  occur?  What  are  the  method  of  preparation  and  properties 
of  the  sulphate  ?  What  is  Scheele's  green  ?  What  are  brass,  gun  metal, 
and  bell  metal  ?  Why  is  silver  and  gold  coinage  alloyed  ? 


LEAD.  297 


LECTURE  LXV. 

LEAD. — Reduction  of  Galena. — Relations  of  Lead  to  Wa- 
ter.—  The  Oxides  of  Lead. — Detection  of  Lead. — BIS- 
MUTH. —  SILVER.  — Amalgamation. — Crystallization.- — 
Cupellation. — Properties  of  Silver. — Salts  of  Silver. 

LEAD.    Pb  =  103-6. 

LEAD  occurs  under  various  mineral  forms,  but  the  most 
valuable  one  is  galena,  a  sulphuret.  From  this  it  is  read- 
ily obtained.  The  galena,  by  roasting  in  a  reverberatory 
furnace,  becomes  partly  converted  into  sulphate  of  lead  ; 
the  contents  of  the  furnace  are  then  mixed,  the  tempera- 
ture raised,  and  the  sulphate  and  sulphuret  produce  sul- 
phurous acid  and  metallic  lead,  the  action  being 
PbO,  SO3  +  P1>S  ...  =  ...  2SOa-  +  Pb,. 

Lead  is  a  soft  metal,  of  a  bluish- white  color.  Its  spe- 
cific gravity  is  11*381.  It  melts  at  612°  F.,  and  on  the 
surface  of  the  molten  mass  an  oxide  (dross)  rapidly  forms. 
At  common  temperatures  it  soon  tarnishes.  In  the  act 
of  solidifying  it  contracts,  and  hence  is  not  fit  for  castings. 
It  possesses,  at  common  temperatures,  the  welding  prop- 
erty ;  two  bullets  will  cohere  if  fresh-cut  surfaces  upon 
them  are  brought  in  contact.  Under  the  conjoint  influ- 
ence of  air  and  water  lead  is  corroded,  a  white  crust  of 
carbonate  forming.  But  when  there  are  contained  in  the 
water  small  quantities  of  salts,  such  as  sulphates,  these 
form  with  the  lead  insoluble  bodies,  which,  coating  its 
surface  over,  protect  it  from  farther  destruction.  For 
this  reason,  lead  pipe  can  be  used  for  distributing  water 
in  cities  without  danger.  Lead  is  one  of  the  least  tena- 
cious of  the  metals.  The  tartrate  of  lead  calcined  in  a 
tube  yields  one  of  the  best  pyrophori.  On  bringing  it 
into  the  air  at  common  temperatures,  it  spontaneously 
ignites. 

Of  the  compounds  of  lead,  the  following  are  some  of 
the  more  important : 

Under  what  form  does  lead  chiefly  occur?  How  is  galena  reduced? 
Why  can  not  lead  be  used  for  castings  ?  What  is  the  action  of  pure  wa- 
ter, and  water  containing  salts,  upon  it? 


298  COMPOUNDS    OF    LEAD. 

• 

Protoxide  of  lead PbO     =111-613. 

Sesquioxide  " P£2O3  =  231-239. 

Peroxide  " PbO2    =  119-626. 

Bed  oxide  " P63O4  =  342-852. 

Chloride  " PbCl    =  139-62. 

Iodide  " Pbl      =229-9. 

Sulphuret  " PbS      =  119'7. 

The  protoxide  is  made  by  heating  lead  in  the  air ;  it  ia 
u  yellow  body,  which  fuses  at  a  bright  red  heat.  In  the 
first  state  it  is  called  massicot ;  in  the  latter,  litharge.  It 
yields  a  class  of  salts,  being  a  base.  It  is  slightly  soluble 
in  water.  The  peroxide  is  made  from  red  lead  by  di- 
gesting it  with  nitric  acid,  which  dissolves  out  the  protox- 
ide, and  leaves  the  substance  as  a  puce  colored  powder. 
The  red  oxide,  or  red  lead,  is  made  by  calcining  lead  in 
a  current  of  air  at  600°  or  700°  F.  It  is  used  in  the 
manufacture  of  flint  glass.  The  chloride  is  made  by  the 
action  of  hot  hydrochloric  acid  on  protoxide  of  lead  :  on 
cooling,  it  is  deposited  in  crystals.  The  iodide  is  formed 
when  any  soluble  iodide  is  added  to  a  protosalt  of  lead  ; 
it  is  a  beautiful  yellow  precipitate,  soluble  in  boiling 
water,  forming  a  colorless  solution,  which,  on  cooling,  de- 
posits golden  crystals.  The  sulphuret  is  galena  ;  it  crys- 
tallizes in  cubes,  and  has  a  high  metallic  lustre. 

Lead  is  easily  detected  by  sulphureted  hydrogen,  which 
throws  it  from  its  solutions  as  a  deep  brown  or  black  pre- 
cipitate, and  by  the  iodide  of  potassium  or  chromate  of 
potash,  which  gives  with  it  a  yellow  precipitate.  Sul- 
phuric acid  yields  with  its  salts  a  white  insoluble  sulphate 
of  lead. 

SALTS  OF  THE  PROTOXIDE  OF  LEAD. 
Carbonate  of  Lead — White  Lead — Ceruse. — This  salt 
forms  as  a  white  precipitate  when  an  alkaline  carbonate 
is  added  to  a  solution  of  a  salt  of  lead.  Large  quantities 
of  it  are  consumed  in  the  arts  as  white  paint.  For  com- 
merce it  is  procured  by  mixing  litharge  with  water  con- 
taining a  small  proportion  of  acetate  of  lead ;  carbonic 
acid  gas  is  then  sent  over  it,  and  the  carbonate  rapidly 
forms.  It  is  also  made  by  exposing  metallic  lead  in 
plates  to  the  action  of  the  vapor  of  vinegar,  air,  and  moist- 
ure, the  metal  becoming  oxydized  and  carbonated. 

"What  is  massicot  ?  How  is  it  prepared  ?  What  is  litharge  ?  How 
is  the  peroxide  prepared?  How  is  minium  made?  How  may  lead  be 
detected  ?  Mention  some  of  the  methods  by  which  white  lead  may  be 
made. 


BISMUTH. SILVER.  299 

Nitrate  of  Lead  may  be  formed  by  dissolving  litharge 
in  dilute  nitric  acid ;  it  crystallizes  in  opaque  white  octa- 
hedrons, which  dissolve  in  seven  or  eight  times  their 
weight  of  cold  water.  They  contain  no  water  of  crystal- 
lization, and  are  decomposed  at  a  red  heat,  as  stated  in 
the  description  of  nitrous  acid.  By  the  action  of  ammo- 
nia, three  other  nitrates  of  lead  may  be  obtained. 

Among  the  alloys  of  lead  are  the  soft  solders.  Two 
parts  of  lead  and  one  of  tin  constitute  plumber's  solder ; 
one  of  lead  and  two  of  tin,  fine  solder. 

BISMUTH.    Bi  =71-07. 

BISMUTH  is  found  both  native  and  as  a  sulphuret.  It  is 
of  a  reddish  color,  melts  at  497°,  and  may  be  obtained  in 
beautiful  cubic  crystals  by  cooling  a  quantity  of  it  until 
solidification  commences,  then  breaking  the  surface  crust 
and  pouring  out  the  fluid  portion. 

When  bismuth  is  dissolved  in  nitric  acid,  and  the  solu- 
tion poured  into  water,  the  white  subnitrate  is  deposited, 
once  used  as  a  cosmetic  ;  when  this  is  washed,  and  sub- 
sequently heated,  the  protoxide  is  left.  There  is  also  a 
peroxide. 

Fusible  metal  is  an  alloy  of  eight  parts  of  bismuth,  five 
of  lead,  and  three  of  tin ;  it  melts  below  the  boiling  point 
of  water,  and  may  be  obtained  in  crystals. 

SILVER.    ^  =  108-31. 

SILVER  is  found  native,  and  as  a'sulphuret  and  a  chlo- 
ride, occurring,  also,  with  a  variety  of  other  metals,  and 
in  small  proportion  with  galena.  When  disseminated  as 
a  metal  through  ores,  it  may  be  collected  from  them  by 
amalgamation  with  quicksilver,  and,  on  distilling,  the 
quicksilver  is  driven  off. 

When  it  is  obtained  from  the  sulphuret,  that  ore  is 
roasted  with  common  salt,  which  changes  it  into  a  chlo- 
ride. This,  with  the  impurities  with  which  it  may  be 
associated,  is  put  into  barrels,  which  revolve  on  an  axis, 
along  with  water,  pieces  of  iron,  and  metallic  mercury ; 
j;he  iron  reduces  the  chloride  to  the  metallic  state,  and 
the  silver  amalgamates  with  the  mercury.  This  is  washed 
from  the  impurities,  strained  through  a  bag  to  separate 

"What  change  does  the  nitrate  undergo  at  a  red  heat  ?  Of  what  are  the 
common  solders  composed  ?  What  are  the  properties  of  bismuth  ?  What 
is  fusible  metal?  Under  what  forms  does  silver  commonly  occur  ?  How 
is  it  reduced  from  the  sulphuret  I 


300  CRYSTALLIZATION. CUPELLATION. 

the  excess  of  mercury,  and  the  residue  is  driven  off'  by 
distillation. 

The  extraction  of  silver,  when  it  occurs  in  small  quan- 
tity with  lead,  has  been  recently  much  improved  by  the 
introduction  of  the  process  of  crystallization.  It  depends 
upon  the  fact  that  an  alloy  of  lead  and  silver  is  more  fusi 
ble  than  lead.  A  large  quantity  of  argentiferous  lead  is 
melted  and  allowed  to  cool.  As  the  setting  goes  on,  the 
first  portions  which  solidify  are  pure  lead ;  they  may  be 
removed  by  iron  colanders,  and  by  continuing  the  process 
there  is  finally  left  a  portion  containing  all  the  silver. 
This  is  exposed  to  a  red  heat,  and  a  stream  of  air  direct- 
ed over  it ;  oxydation  of  the  lead  takes  place,  and  the 
litharge  is  removed  by  the  blast,  the  process  being  finally 
completed  by  cupellation. 

A  cupel  is  a  shallow  dish  made  of  bone  ashes,  and  is 
very  porous.  In  this,  if  an  alloy  of  lead  and  silver  be  heat- 
ed with  access  of  air,  the  lead  oxydizes,  and,  melting  into 
a  glass,  soaks  into  the  cupel,  or  may  be  driven  from  the 
surface  by  a  blast  of  air  directed  from  a  bellows.  At  the 
same  time,  any  copper  or  other  base  metal  oxydizes  and 
is  removed  along  with  the  lead.  The  completion  of  the 
process  is  indicated  by  the  silver  .assuming  a  certain  brill- 
iancy, or  flashing,  as  the  workmen  term  it. 

Silver  is  a  white  metal  capable  of  receiving  a  brilliant 
polish.  It  is  malleable  and  ductile,  an  excellent  conduct- 
or of  heat  and  electricity.  Its  specific  gravity  is  10-5.  It 
melts  at  1873°  F.,  and  when  melted  absorbs  a  large  quan- 
tity of  oxygen,  giving  it  out  again  as  soon  as  it  solidifies, 
and  assuming  a  frosted  or  porous  appearance.  The  pres- 
ence of  a  minute  quantity  of  copper  prevents  this  effect. 
Silver  is  so  soft  that,  for  making  plate  or  coins,  it  requires 
to  be  alloyed  with  a  portion  of  copper  ;  from  this  it  may 
be  purified  by  dissolving  it  in  nitric  acid,  and  precipitating 
the  silver  as  chloride  by  a  solution  of  common  salt.  Sil- 
ver shows  little  disposition  to  unite  with  oxygen,  though 
it  tarnishes  readily  by  the  action  of  sulphureted  hydrogen. 
It  yields  three  oxides,  but  of  its  compounds  the  following* 
are  the  most  important : 

What  is  the  process  of  amalgamation  ?  What  is  the  process  of  crystal- 
lization ?  What  is  the  process  of  cupellation  ?  What  are  the  properties 
of  silver  ?  Why  does  it  frequently  require  to  be  alloyed  with  copper  ? 
What  remarkable  relation  does  it  possess  to  oxygen  ? 


COMPOUNDS    OF    SILVER.  301 

Protoxide  of  silver  .    .     .     .  AgO  =  116-323. 

Chloride  "  ....  AgCl  =  143'78. 

Iodide  "  ....  Agl    =234-48. 

Sulphuret          "  ....  AgS  =124-43. 

The  protoxide  may  be  made  by  the  action  of  caustic 
potash  on  a  solution  of  nitrate  of  silver,  or  by  boiling  re- 
cently-prepared chloride  in  potash.  It  is  a  dark  powder, 
which  may  be  reduced  by  heat  alone.  The  chloride  is 
sometimes  found  native,  as  horn-silver,  and  may  be  made 
by  precipitation  from  the  nitrate  by  hydrochloric  acid, 
or  a  soluble  chloride.  Like  the  iodide,  it  turns  dark  011 
exposure  to  the  indigo  rays,  and  hence  is  used  in  photo- 
genic drawing.  The  sulphuret  is  produced  whenever  sul- 
phureted  hydrogen  acts  on  oxide  of  silver,  or  even  metal- 
lic silver ;  it  is  a  black  compound. 

Silver  is  easily  detected  by  precipitation  as  a  chloride  : 
a  curdy,  white  precipitate,  insoluble  in  water,  but  soluble 
in  ammonia.  It  turns  dark  on  exposure  to  the  sun. 

SALTS  OF  THE  PROTOXIDE  OF  SILVER. 

Nitrate  of  Silver — Lunar  Caustic — procured  by  dissolv- 
ing silver  in  .nitric  acid,  diluted  with  twice  its  weight  of  wa- 
ter. It  crystallizes  in  tables  which  are  not  deliquescent  and 
contain  no  water  of  crystallization.  It  enters  into  fusion 
at  426°  F.,  but  at  higher  temperatures  undergoes  decom- 
position. It  is  frequently  cast  into  small  sticks  and  used  by 
surgeons  as  a  cautery.  It  is  soluble  in  its  own  weight  of 
cold  and  half  its  weight  of  hot  water,  and,  when  in  contact 
with  organic  matter,  turns  black  in  the  rays  of  the  sun. 

Ammoniuret  of  Silver — Berthollet' }s Fulminating  Silver — 
is  formed  by  digesting  precipitated  oxide  of  silver  in  am- 
monia. It  explodes  with  the  utmost  violence  under  the 
feeblest  friction,  with  the  evolution  of  nitrogen  and  the 
vapor  of  water. 

How  may  the  protoxide  be  prepared  ?  What  changes  do  the  chloride 
and  iodide  exhibit  under  the  influence  of  light  ?  How  may  silver  be  de- 
tected ?  How  is  lunar  caustic  made  ? 

C  c 


302  MERCURY. 


LECTURE  LXVI. 

MERCURY. — Process  of  Reduction. —  The  Liquid  State  of. 
— Its  Oxides. —  Calomel  and  Corrosive  Sublimate. — De- 
tection of  Mercury. — Its  Salts. — Amalgams. — GOLD. — 
Chloride  of. — Purple  of  Cassius. — PALLADIUM. — PLA- 
TINUM.— Its  Catalytic  Effects. — Platinum  Black. — IRID- 
IUM. — RHODIUM. 

MERCURY.     fl£  =  202. 

MERCURY  may  be  obtained  from  the  bisulphuret  (cin 
nabar)  by  distillation  with  iron  filings.     It  is  also,  to  a 
certain  extent,  found  native. 

The  striking  characteristic  of  mercury  is  its  liquid  condi- 
tion. Its  melting  point  is  the  lowest  of  that  of  any  of  the 
metals,  being  — 39°  F.  Its  specific  gravity  at  47°  F.  is 
13-545.  It  boils  at  662°  F.  Kept  at  that  temperature  in 
the  air  for  a  length  of  time,  it  produces  red  oxide ;  but 
at  common  temperatures  it  is  not  acted  on  by  the  air.  It 
may  be  freed  from  impurities  for  the  purposes  of  the  lab- 
oratory, by  being  kept  in  contact  with  dilute  nitric  acid. 
It  gives  the  following  compounds  of  interest : 


Protoxide  of  mercury 
Peroxide  " 

Protochloride      " 
Bichloride  " 

Protosiilphuiret  " 
Bisulphuret        " 


.  HgO     =210-013 
.  Ego*  =  218-026. 
.  HgCl    —  237-42. 
.  HgCl*  = 
HgS     = 


218-1. 
=  234-2. 


The  protoxide  may  be  made  by  triturating  calomel 
with  potash  water  in  a  mortar.  It  is  a  black  powder, 
"which  is  decomposed  by  light  or  any  of  the  reducing  agents. 
The  peroxide  may  be  formed,  as  stated  above,  by  the  ac- 
tion of  air  on  hot  mercury,  but  more  easily  by  dissolving 
mercury  in  nitric  acid  and  evaporating  and  heating  the 
salt  until  no  more  fumes  of  nitrous  acid  are  evolved.  It  is 
a  red  powder,  and  when  warmed  becomes  almost  black, 
the  color  returning  as  the  temperature  descends.  Like 
the  former,  it  is  a  base,  and  yields  a  class  of  salts. 

The  Protochloride,  or  Calomel,  may  be  made  by  adding 
hydrochloric  acid  to  the  protonitrate  of  mercury,  or  by  sub- 
Under  what  forms  does  mercury  commonly  occur?  What  is  the  most 
striking  property  of  this  metal  ?  How  may  it  be  purified  ?  What  are 
the  properties  of  the  protoxide  and  peroxide  ?  What  is  calomel  ? 


COMPOUNDS  OF  MERCURY.  303 

liming  a  mixture  of  bichloride  of  mercury  and  mercury. 
It  is  a  white  powder,  insoluble  in  water,  and  darkens 
slowly  by  exposure  to  sunshine.  The  bichloride  (or  Cor- 
rosive Sublimate)  is  formed  when  mercury  burns  in  chlo- 
rine gas,  but  more  economically  by  sublimation  from  a 
mixture  of  persulphate  of  mercury  and  common  salt.  It 
is  a  heavy,  white,  crystalline  body,  soluble  in  water,  has 
a  metallic  taste,  and  is  poisonous.  The  antidote  for  it  is 
albumen  (the  white  of  an  egg). 

Of  the  sulphurets  of  mercury,  the  protosulphuret  is 
black,  and  the  bisulphuret  commonly  red ;  in  this  case  it 
passes  in  commerce  under  the  name  of  vermilion,  and  is 
used  as  a  paint.  It  can  be  obtained,  however,  quite  black, 
a  peculiarity  already  observed  in  the  case  of'  the  perox- 
ide, and  still  more  strikingly  in  the  biniodide,  which  may 
be  sublimed  in  beautiful  yellow  crystals,  which  become 
of  a  splendid  scarlet  color  by  merely  being  touched. 

Mercury  may  be  detected  by  being  precipitated  from 
its  soluble  combinations  by  metallic  copper  as  a  metal. 
Its  salts,  either  alone  or  with  carbonate  of  soda,  heated  in 
a  tube,  yield  metallic  mercury,  which  volatilizes. 

SALTS  OF  THE  OXIDES  OF  MERCURY. 

Nitrates  of  the  Oxides  of  Mercury. — When  cold  dilute 
nitric  acid  acts  on  mercury  it  gives  rise  to  neutral  or  basic 
protosalts,  as  the  acid  or  mercury  is  in  excess ;  if  the  acid 
be  hot,  a  pernitrate  forms ;  these  salts  are  decomposed  by 
an  excess  of  water,  giving  rise  to  basic  compounds.  The 
neutral  pernitrate  exists  in  solution  only. 

Persulphate  of  Mercury  is  formed  by  boiling  sulphuric 
acid  and  mercury,  and  evaporating  to  dryness.  It  occurs 
in  the  form  of  a  white  granular  mass,  and  is  decomposed 
by  water,  giving  a  yellow  precipitate,  a  subsulphate  call- 
ed Turpeth  Mineral. 

The  alloys  of  mercury  are  called  amalgams  ;  the  amal- 
gam of  tin  is  used  for  silvering  looking-glasses,  and  that 
of  zinc  for  exciting  electrical  machines. 
GOLD.    Au  =  199-2. 

Gold  is  found  native,  and  may  be  obtained  by  washing 

What  is  corrosive  sublimate  ?  What  is  the  antidote  to  it  1  For  what 
purpose  is  the  bisulphuret  employed?  What  change  occurs  to  the  yel- 
low biniodide  when  it  is  touched  ?  How  may  mercury  be  detected  ?  How- 
are  the  protonitrate  and  the  persulphate  prepared  ?  Under  what  forma 
does  gold  occur  ? 


304  GOLD. 

or  by  amalgamation  with  mercury.  It  may  be  purified 
from  silver  by  quartation ;  that  is,  fusing  it  with  three 
times  its  weight  of  silver,  and  then  acting  on  the  mass 
with  nitric  acid.  The  gold  is  left  as  a  dark  powder. 

From  all  other  metals  gold  is  distinguished  by  its  yel- 
low color.  Its  specific  gravity  is  19-3.  It  melts  at  2016° 
F.  It  is  the  most  malleable  of  all  the  metals,  as  is  proved 
by  gold-leaf,  which  may  be  obtained  ^^^Viro  mcn  i*1  thick- 
ness ;  is  not  acted  upon  by  the  air  or  oxygen.  Objects 
of  art  covered  with  it  have  retained  their  brilliancy  for 
thousands  of  years.  No  acid  alone  dissolves  it;  but  it  is 
soluble  in  aqua  regia,  and  also  by  chlorine. 

It  can,  however,  be  made  to  yield  two  oxides,  a  pro- 
toxide and  a  teroxide  ;  and  two  chlorides  having  the  same 
constitution ;  the  terchloride  is  formed  by  the  action  of 
nitromuriatic  acid  (aqua  regia)  on  gold.  When  evapora- 
ted, it  yields  red,  deliquescent  crystals.  Deoxydizing 
agents,  such  as  protosulphate  of  iron,  reduce  it  to  the  me- 
tallic state  ;  this  is  probably  due  to  their  decomposing 
water  and  presenting  hydrogen  to  the  chloride.  Hydro- 
gen gas  decomposes  the  terchloride,  and,  by  heating  it,  it 
first  changes  into  the  protochloride  and  then  into  metallic 
gold.  "With  a  solution  of  tin  it  forms  the  Purple  of  Cas- 
sius.  This  and  the  action  of  protosulphate  of  iron  serve 
as  a  test  for  it. 

PALLADIUM.  Pd  =  53-s. 

Palladium  is  found  associated  with  platinum,  and  is 
best  obtained  from  the  cyanide  of  palladium  by  ignition. 
It  is  a  white  metal,  requiring  a  high  temperature  for  fu- 
sion ;  specific  gravity  11-5.  It  does  not  tarnish  in  the  air, 
is  dissolved  by  nitric  acid  and  aqua  regia,  is  one  of  the 
welding  metals,  and,  when  heated,  acquires  a  purple  oxy- 
dation  like  watch  spring.  It  is  used  to  some  extent  by 
dentists.  Its  compounds  are  not  of  importance. 

PLATINUM.     Ft  =  98-84. 

Platinum  is  found  native,  but  always  associated  with 
other  metals.  It  is  obtained  by  first  forming  a  chloride 
of  platinum  and  ammonium ;  this,  when  ignited,  leaves 

What  is  quartation  ?  "What  are  the  properties  of  this  metal  ?  How 
many  oxides  does  it  yield?  How  is  the  terchloride  prepared ?  What  is 
the  purple  of  Cassius  ?  With  what  metal  is  palladium  generally  associ- 
ated ?  What  are  its  properties  ?  What  superficial  effect  takes  place 
when  it  is  heated  in  the  air  ?  How  is  platinum  obtained  from  its  ores  ? 


PLATINUM.  305 

pure  spongy  platinum,  which  being,  exposed  to  powerful 
pressure,  and  then  alternately  made  white  hot  and  ham- 
mered, becomes  a  solid  mass. 

Platinum  is  a  white  metal.  Its  specific  gravity  is  very 
high,  being  21 '5.  It  can  not  be  melted  in  a  furnace,  but 
fuses  before  the  oxyhydrogen  blow-pipe.  It  is  a  welding 
metal,  and  on  this  fact  its  preparation  depends.  It  is  very 
malleable  and  ductile,  is  not  acted  upon  by  oxygen,  air, 
or  any  acid  alone,  but  dissolves  in  aqua  regia.  It  pos- 
sesses the  extraordinary  property  of  causing  hydrogen 
and  oxygen  to  unite  at  common  temperatures,  an  effect 
which  takes  place  with  remarkable  energy  when  the 
metal  is  in  a  spongy  state.  A  jet  of  hydrogen  falling 
upon  spongy  platina  in  the  air  makes  it  red  hot,  and  pres- 
ently after  the  gas  takes  fire.  It  also  brings  about  the 
rapid  transformation  of  alcohol  into  acetic  acid,  and  va- 
rious other  chemical  changes. 

If  a  quantity  of  ether  be  poured  into  Ftz- 268- 

a  glass  jar,  Fig.  268,  and  a  coil  of  pla- 
tinum wire,  recently  ignited,  be  intro- 
duced, the  metal  continues  to  glow  so 
•  long  as  any  ether  is  present. 

Platinum  is  invaluable  to  the  chem- 
ist. It  fumishes  a  variety  of  imple- 
ments of  great  value,  and  is  met  with 
under  the  forms  of  crucibles,  tubes, 
wire,  foil,  &c. 

Platinum  Slack  is  prepared  by  slow-  >n^ 
ly  heating  to  212°  a  solution  of  chlo- 
ride of  platinum,  to  which  an  excess  of  carbonate  of  soda 
and  some  sugar  have  been  added.  It  is  a  dark  powder, 
and  possesses  the  property  of  determining  a  variety  of 
chemical  changes  with  much  more  energy  than  platinum 
in  mass. 

Platinum  can  be  caused  to  yield  two  oxides,  which  are 
not  of  any  importance ;  and  two  analogous  chlorides,  of 
which  the  bichloride,  which  is  the  common  platinum  salt, 
is  made  by  dissolving  the  metal  in  nitromuriatic  acid, 

What  is  the  specific  gravity  of  this  metal  ?  By  what  acid  may  it  be 
dissolved  ?  What  remarkable  relations  does  it  possess  to  hydrogen  gas  ? 
Under  its  influence,  what  is  alcohol  transmuted  into  ?  What  is  platinum 
black  ? 

Cc2 


306  IR1D1UM.  -  RHODIUM. 

and  evaporating  to  a.  sirup.     It  is  soluble  in  water  and 
alcohol,  and  is  used  ibr  detecting  the  salts  of  potash. 


IBIDIUM.     Jr 

Iridium  is  associated  with  platinum.  It  is  said  to  have 
been  found  of  specific  gravity  26*00.  Dr.  Hare  has  ob- 
tained it  21-8  ;  it  is,  therefore,  the  heaviest  of  the  metals. 
Its  name  is  derived  from  the  different  colors  (iris)  of  its 
compounds. 

RHODIUM.    £  =  52-2. 

Like  the  former  metal,  rhodium  is  associated  with  the 
platina  ores.  It  is  a  hard  white  metal  ;  its  specific  grav- 
ity is  ll'OO,  and  is  sometimes  used  to  form  tips  to  metal- 
lic pens. 

What  are  the  properties  of  iridium?    What  are  those  of  rhodium? 


PART  IV. 

ORGANIC    CHEMISTRY. 


LECTURE  LXVII. 

Peculiarities  of  Organic  Bodies. —  Their  Constituent  Ele- 
ments.— Prone  to  Decomposition. — Carbon  always  Pres- 
ent.— Compound  Radicals. — Doctrine  of  Substitution. — 
Types. — Action  of  Heat. — Eremacausis. — Propagation 
of  Decay. — Action  of  Acids  and  Alkalies. 

THE  theory  of  molecular  arrangement,  which  has  been 
already  given,  forms  the  foundation  of  organic  chemistry. 
It  asserts  that  the  characters  of  compound  bodies  do  not 
alone  depend  on  the  nature  of  their  constituent  elements, 
nor  even  on  the  relative  amount  of  those  elements ;  but 
that  variation  of  physical  forms  may  result  from  atoms  of 
the  same  name  and  of  the  same  number  arranging  them- 
selves in  subordinate  groups,  which  groups  then  unite 
with  each  other. 

The  leading  ultimate  elements  of  organized  bodies  are 
carbon,  hydrogen,  .nitrogen,  and  oxygen.  Almost  all  or- 
ganic bodies  arise  from  variations  in  the  number  and 
grouping  of  identical  elements. 

Now  a  partial  consideration  of  the  conditions  under 
which  the  theory  of  molecular  arrangement  acts,  exhibits 
to  us  a  most  striking  difference  in  the  nature  of  the  com- 
pounds formed  upon  its  principles  and  the  compounds 
heretofore  described  as  examples  of  inorganic  chemistry. 
In  the  one,  peculiarity  of  grouping  is  the  grand  feature  ; 
in  the  other,  the  character  of  the  combining  elements. 
Urea  differs  from  the  cyanate  of  ammonia  in  the  arrange- 
ment of  its  constituents  only ;  but  the  leading  mark  of  dis- 
tinction between  sulphuric  and  phosphoric  acids  is,  that 
the  one  contains  sulphur  and  the  other  phosphorus. 

The  number  of  substances  which,  besides  the  four  men- 

On  what  do  the  characters  of  compound  bodies  depend  ?  Of  what  four 
leading  elementary  bodies  are  organic  substances  chiefly  composed  ?  In 
what  striking  respect  do  these  substances  differ  from  inorganic  ones  ? 


308  CHARACTERS    OF    ORGANIC    BODIES. 

tioned  above,  enter  into  the  composition  of  organic  bodies 
is  very  limited.  Among  such  may  be  mentioned  potash, 
soda,  lime,  magnesia,  oxide  of  iron,  chlorine,  fluorine,  sul- 
phur, phosphorus,  and  silica.  Some  of  those  bodies,  such 
as  alumina,  which  appear  to  take  the  lead  in  inorganic 
productions,  are  here  scarcely  seen. 

While  the  laws  of  inorganic  chemistry  appear  to  be 
fully  in  operation  as  respects  the  bodies  ori  the  study  of 
which  we  are  now  entering,  there  are  some  peculiarities 
which  deserve  to  be  pointed  out.  The  remarkable  insta- 
bility, or  proneness  to  decomposition,  which  so  many  of 
them  exhibit,  generally  tends  to  the  production  of  second- 
ary compounds  of  a  much  more  stable  nature.  At  a  red  heat 
all  organized  bodies  are  decomposed  ;  and  as  the  ele- 
ments of  which  they  consist  are  endowed  with  the  most 
energetic  affinities,  any  extensive  elevation  of  tempera- 
ture tends  to  impress  upon  them  a  change.  "With  but  few 
exceptions,  the  attempts  which  have  hitherto  been  made 
to  produce  them  artificially  have  been  abortive  ;  but  this  rs, 
probably,  rather  due  to  our  want  of  knowledge  than  any 
intrinsic  impossibility  in  effecting  such  combinations. 

With  the  exception  of  a  few  bodies,  such  as  ammonia, 
which,  in  point  of  fact,  belong  rather  to  inorganic  chem- 
istry, all  organized  bodies  contain  carbon.  Of  late,  by  in- 
direct processes,  chemists  have  succeeded  in  obtaining 
pseudo- organized  compounds,  into  the  constitution  of 
which  such  bodies  as  platinum  and  arsenic  enter. 

In  inorganic  chemistry  we  see  a  constant  disposition  to 
the  binary  form  of  union  :  a  disposition  which  is  well  rep- 
resented by  the  electro-chemical  theory.  Thus,  potassi- 
um unites  with  oxygen,  two  bodies  together,  to  form  pot- 
ash ;  and  this,  again,  with  sulphuric  acid,  two  bodies  to- 
gether, to  form  sulphate  of  potash.  In  very  many  instan- 
ces, the  same  thing  can  be  traced  in  organic  chemistry ; 
only  here,  instead  of  having  such  bodies  as  chlorine  or 
iodine,  potassium  or  sodium  to  deal  with,  we  find  com- 
pound bodies  which  discharge  analogous  functions.  These 
bodies  go  under  the  name  of  compound  radicals.  They 
may  be  divided  into  distinct  groups,  some  discharging  the 

What  other  elements  are  found  among  organic  bodies  ?  In  their  de- 
composition, what  do  they  generally  produce  ?  Can  any  of  them  with- 
stand a  red  heat?  Can  they  be  formed  by  artificial  means?  What  is 
meant  by  compound  radicals  ? 


COMPOUND    RADICALS.  309 

duty  of  electro-negative,  some  of  electro-positive,  and 
some  of  indifferent  bodies.  In  several  cases  they  have 
been  insulated,  but  in  others  they  remain  as  yet  as  ideal 
or  hypothetical  bodies. 

Table  of  Compound  Radicals. 


Amidogen. 
Oxalyle. 
Cyanogen. 
F  errocy  anogen. 
Ferridcyanogen. 
Cobaltocyanogen. 
Chromocy  anogen. 
Platiuocy  anogen. 

Iridiocyanogen. 
Sulphocyanogen. 
Mellone. 
Uryle. 
Benzyle. 
Salicyle. 
Cinnaniyle. 
Ethyle. 

Acetyle. 
Kakodyle. 
Methyle. 
Formyle. 
Cetyle. 
Amyle. 
Glyceryle. 

The  qualities  of  bodies  depending  as  much  on  the  mode 
of  arrangement  of  their  constituent  particles  as  on  the 
chemical  nature  of  those  particles,  it  has  been  found  con- 
venient to  arrange  them  in  groups,  according  to  their 
type  of  structure ;  thus,  for  instance,  in  the  former  de- 
partment of  chemistry,  such  bodies  as  hydrochloric,  hy- 
driodic,  hydrobromic  acids  may  be  arranged  together  as 
belonging  to  one  type ;  and  from  the  first  of  these  all  the 
rest  may  be  conceived  as  arising,  by  substituting  an  atom 
of  iodine,  bromine,  fluorine,  &c.,  for  the  atom  of  chlorine 
which  it  contains. 

The  bodies  which  can  thus  be  substituted  for  each 
other  appear  to  have  certain  relationships ;  for  the  sub- 
stitution of  a  given  substance  can  not  take  place  indiscrim- 
inately by  all  other  bodies.  As  a  general  rule,  in  inor- 
ganic combinations,  electro-negative  bodies  can  only  be 
substituted  by  electro-negative,  and  electro-positive  by 
electro-positive.  But  many  of  the  most  prominent  cases 
in  organic  chemistry  are  precisely  the  reverse.  In  them, 
for  example,  we  find  chlorine,  a  powerful  electro-nega- 
tive, taking  the  place  of  hydrogen,  an  equally  powerful 
electro-positive  body,  and,  in  the  compound,  discharging 
all  its  functions.  For  these  reasons,  it  has  been  supposed 
that  the  electro-chemical  theory  fails  to  furnish  any  ex- 
planation ;  but  I  have  proved  that  chlorine,  like  many 
other  bodies,  can  assume  different  allotropic  states  ;  at  one 
time  being  an  active  electro-negative  body,  and  at  an- 
other quite  passive.  Moreover,  it  ought  not  to  be  for- 

What  compound  radicals  are  known  ?  Under  what  circumstances  can 
bodies  be  substituted  for  each  other?  Is  there  any  difference  in  this  re- 
bpect  between  inorganic  and  organic  bodies  ? 


310  DESTRUCTION    OF    ORGANIC   COMPOUNDS. 

gotten  that  hydrogen,  in  relation  to  carbon,  is  as  much  an 
electro-negative  body  as  chlorine  itself. 

A  chemical  type  is,  therefore,  a  system,  or  group  of 
atoms  of  a  certain  number,  arranged  in  a  certain  relation- 
ship with  each  other.  From  this  each  atom  may  be  dis- 
placed, and  one  of  another  kind  substituted  in  its  stead; 
and  this  may  be  carried  forward  until  not  one  of  the  orig- 
inal atoms  is  left,  the  new  group  officiating  in  all  respecta 
like  its  predecessor.  But  should  one  of  the  atoms  be 
displaced,  and  no  new  one  substituted  for  it,  then,  the  re- 
maining atoms  changing  their  position,  the  type  is  broken 
up  and  a  new  one  is  the  result. 

Organic  compounds,  being  for  the  most  part  composed 
of  carbon,  hydrogen,  nitrogen,  and  oxygen,  exhibit  a  con- 
stant tendency  to  break  up  into  subordinate  groups,  and 
eventually  to  give  rise  to  the  production  of  the  simpler 
binary  bodies,  carbonic  acid,  water,  and  ammonia.  The 
carbon  constantly  inclines  to  unite  with  oxygen  to  form 
carbonic  acid,  the  hydrogen,  in  the  same  manner,  to  form 
water,  or,  with  the  nitrogen,  to  produce  ammonia ;  and 
these  tendencies  may  be  satisfied  in  a  variety  of  ways. 
Elevations  of  temperature  in  the  open  air  at  once  give 
rise  to  carbonic  acid,  water,  and  free  nitrogen;  or  if  in 
close  vessels  out  of  the  contact  of  air,  to  an  extensive  se- 
ries of  compounds,  differing  in  each  case  with  the  sub- 
stance exposed,  and  of  a  less  complex  constitution.  Even 
in  the  air,  at  common  temperatures,  a  slow  action  often 
goes  on,  as  in  the  decay  of  wood  or  the  souring  of  wine  ; 
hence  called  eremacausis  (slow  combustion). 

When  a  combustible  substance  is  ignited  in  the  air  at 
one  point,  the  burning  presently  spreads  throughout  the 
whole  mass;  and  in  the  slow  combustion,  eremacausis, 
the  same  takes  place.  A  substance  undergoing  such  a 
change,  if  placed  in  contact  with  another  capable  of  un- 
dergoing it,  propagates  its  effect  throughout  the  whole 
mass.  For  this  reason,  the  decay  of  yeast,  a  ferment,  im- 
presses a  metamorphosis  on  sugar,  compelling  it  to  give 
off  carbonic  acid  gas  ;  and  putrefaction  of  fresh  meat  is  eas- 
ily brought  on  by  the  contact  of  putrid  animal  matter. 

What  is  a  chemical  type  ?  Under  what  circumstances  do  new  types 
result  ?  "What  are  the  binary  bodies  eventually  produced  ?  What  is  the 
result  of  elevation  of  temperature  in  the  open  air  ?  What  in  close  vessels  1 
What  is  meant  by  eremacausis  ?  In  what  respect  does  -eremacausis  re- 
semble common  combustion  ? 


THE    NON-NITHOGENIZED    BODIES.  311 

Nitric,  sulphuric,  and  other  strong  acids  impress  striking 
changes  when  heated  with  organic  matters  ;  thus,  when 
the  former  acts  on  starch,  oxalic  acid  is  formed;  when 
sulphuric  acid  acts  on  oxalic,  it  totally  destroys  it,  resolv- 
ing it  into  carbonic  acid,  carbonic  oxide,  and  water.  In 
the  same  manner,  also, basic  bodies  produce  striking  chang- 
es, generally  giving  rise  to  the  production  of  acids,  and  the 
evolution  of  hydrogen  and  ammonia. 

In  the  present  state  of  organic  chemistry,  it  is  impos- 
sible to  present  a  perfect  system  of  arrangement,  as  in  in- 
organic chemistry,  or  one  approaching  to  the  finish  of  that 
department.  The  course,  therefore,  which  I  shall  now 
take  is  recommended  rather  for  its  usefulness  in  facilita- 
ting study  than  for  the  propriety  of  its  classification. 


LECTURE  LXVIII. 

THE  NON-NITROGENIZED  BODIES. —  The  Starch  Group. — 
Starch. — Action  of  Iodine. —  Various  Forms  of  Starch. 
— Production  of  Dextrine. — Action  of  Diastase. — Leio- 
come.  —  Can  e  Sugar. — Glucose. — Distinction  between 
Cane  and  Grape  Sugar. — Milk  Sugar. — Gum. — Lig 
nine. 

THE  non-nitrogenized  bodies,  which  we  shall  first  con- 
sider, are  characterized  by  the  peculiarity  that  they  form 
a  group,  each  member  containing  twelve  atoms  of  carbon, 
united  with  hydrogen  and  oxygen  in  the  proportions  to 
form  water.  They  are  for  the  most  part  indifferent  bod- 
ies. 

The  Starch  Group. 
Starch 

Cane  sugar  (crystallized)     .     . 
Grape  sugar 
Milk  sugar 

Gum Ci2//uOu. 

Lignine CizH%  Os. 

Sec.  &.c. 

Starch — Fecula  (C13HloOi0) — is  found  abundantly  in  the 
vegetable  kingdom,  and  may  be  obtained  from  potatoes 

What  is  the  effect  of  strong  acids  and  alkalies  on  organic  bodies  ?  How 
many  carbon  atoms  does  each  member  of  the  amyle  group  contain?  In 
what  proportion  are  their  oxygen  and  hydrogen?  Mention  some  of  the 
chief  bodies  of  this  group.  From  what  sources,  and  in  what  manner,  w 
starch  obtained  ? 


312  VARIETIES    OF   STARCH. 

by  rasping  and  washing  the  mass  upon  a  sieve,  the  starch 
being  carried  off  by  the  water.  It  may  also  be  obtained 
from  flour  by  making  it  into  a  paste  with  water  and  then 
washing  it.  The  starch  separates,  and  gluten  is  left  be- 
hind. 

It  is  a  white  substance,  commonly  met  with  in  irregu- 
lar prismatic  masses,  which  shape  it  assumes  while  drying. 
It  is  insoluble  in  cold  water,  and  also  in  alcohol,  and  con- 
sists of  granules  of  different  sizes,  as  it  is  derived  from 
different  plants,  those  of  the  potato  being  about  the  two 
hundred  and  fiftieth  of  an  inch  in  diameter. 

When  starch  is  heated  in  water,  the  covering  mem- 
brane of  each  granule  bursts  open,  and  the  interior  matter 
dissolves  out.  If  the  proportion  of  starch  be  considerable, 
the  whole  forms  a  jelly-like  mass,  which  may  be  dried  in 
a  yellowish  body,  having  the  same  constitution  as  starch 
itself.  Gelatinous  starch  passes  under  the  name  of  Ami- 
dine. 

With  free  iodine,  starch  strikes  a  deep  blue  color. 
When  water  containing  this  compound  is  heated  to  212° 
F.,  the  color  totally  disappears,  and  is  not  restored  on  cool- 
ing ;  but  if  the  source  of  heat  be  removed  as  soon  as  the 
color  disappears,  and  before  the  temperature  reaches  212° 
F.,  the  color  returns.  Starch  and  iodine  constitute  an  ex- 
ceedingly delicate  test  for  each  other. 

In  commerce,  starch  is  found  under  various  modifica- 
tions, such  as  Arrow-root,  Tapioca,  Cassava,  Sago.  It 
forms  an  important  article  of  respiratory  food.  Inuline, 
which  is  derived  from  the  dahlia  and  other  plants,  is  a  sub- 
stance approaching  starch  in  many  respects. 

When  starch  is  boiled  in  water  with  a  small  quantity  of 
sulphuric  acid,  it  changes  into  Dextrine,  a  substance  of  the 
same  composition  ;  the  acid  being  subsequently  removed 
by  carbonate  of  lime  and  filtration,  that  body  is  procured 
on  evaporation  as  a  gummy  mass.  But  if  the  ebullition 
be  continued  for  a  longer  time,  the  dextrine  disappears 
and  grape  sugar  comes  in  its  stead.  Starch  may  also  be 
converted  into  grape  sugar  by  the  action  of  a  peculiar 
ferment,  Diastase,  which  is  contained  in  an  infusion  of 


What  is  the  size  of  its  granules  ?  What  is  the  effect  of  hot  water  on 
it  ?  What  is  amidine  ?  What  is  the  action  of  iodine  on  starch  ?  Mention 
gome  other  varieties  of  starch.  How  is  it  converted  into  dextrine  ?  How 
into  grape  sugar?  What  is  diastase  ? 


CANE    SUGAR.  313 

malt.  Gelatinous  starch  may,  in  the  course  of  a  few  min- 
utes, at  160°  F.,  be  converted  into  dextrine  by  this  sub- 
stance, and  soon  after  into  sugar.  In  either  of  these  cases 
the  presence  of  atmospheric  air  is  not  required  ;  the  final 
action  being  that  the  starch  simply  assumes  three  atoms  of 
water,  and  becomes  converted  into  grape  sugar. 

When  baked  at  a  temperature  of  about  400°  F.,  starch 
becomes  soluble  in  water,  and  passes  in  commerce  under 
the  name  of  British  Gum,  or  Leiocome. 

Cane  Sugar  (C^H^O^-}-2HO)  is  found  abundantly  in 
the  juices  of  many  plants,  and  is  chiefly  extracted  for  com- 
mercial purposes  from  the  sugar-cane,  which,  being  crushed 
between  rollers,  yields  a  juice,  which  is  mixed  with  lime 
and  boiled ;  a  coagulum  having  been  removed  from  it,  it 
is  rapidly  evaporated  at  as  low  a  temperature  as  possible, 
and  then  crystallized.  In  tliis  state,  after  a  brownish  sir- 
up, molasses,  has  drained  from  it,  it  passes  in  commerce  un- 
der the  name  of  Muscovado,  or  brown  sugar.  This  is  pu- 
rified by  boiling  in  water  with  albumen,  which,  coagulat- 
ing, separates  many  of  the  impurities  ;  the  solution  is  then 
decolorized  by  animal  charcoal,  evaporated,  solidified  in 
conical  vessels,  and,  being  washed  with  a  little  clean  sirup, 
is  thrown  into  commerce  as  loaf-sugar.  Sugar  is  also  ob- 
tained from  the  sap  of  the  maple-tree,  and  from  beet-root. 

From  a  strong  solution  Sugar  crystallizes  in  rhombic 
prisms,  which  are  colorless;  they  pass  under  the  name  of 
Sugar  Candy.  It  is  soluble  in  one  third  its  weight  of  cold 
water,  and  in  any  quantity  of  hot.  It  has  a  sweet  and 
proverbially  characteristic  taste.-  When  heated,  it  melts, 
and  gives  rise  to  a  yellowish,  transparent  body,  called 
Barley  Sugar.  But  if  kept  at  a  temperature  of  630°  F., 
it  turns  of  a  reddish-brown  color,  constituting  Caramel. 
Sugar  unites  with  various  bodies,  such  as  lime  and  oxide 
of  lead,  and  with  common  salt  yields  a  crystallized  prod- 
uct. By  caseine  it  is  transformed  into  lactic  acid. 

Grape  Sugar — Fruit  Sugar — Glucose — Starch  Sugar 
— Diabetic  Sugar  (C12H14:O14} — is  the  substance  just  de- 
scribed as  arising  from  the  transmutation  of  starch  under 
the  influence  of  acids.  It  occurs  naturally  in  many  vege- 
table juices  and  in  honey. 

What  is  its  action  on  starch?     How  is  British  ^um  formed?    .From 
what  sources,  and  by  what  means,  is  cane  sugar  derived  ?    What  are  its 
properties?     By  what  means  is  caramel  formed? 
D  D 


314  GHAPE  AND  MILK  SUGAR. 

Compared  with  cane  sugar,  it  is  much  less  soluble  in 
water,  and  less  disposed  to  crystallize.  It  requires  l£ 
parts  of  water  for  solution.  It  may  be  distinguished  by 
its  action  with  caustic  alkalies  and  sulphuric  acid,  the  form- 
er turning  it  brown  and  the  latter  dissolving  it  without 
blackening,  while  cane  sugar  is  little  acted  on  in  the  form- 
er instance,  and  blackened  in  the  latter.  The  two  vari- 
eties may  also  be  distinguished  by  being  mixed  with  a  so- 
lution of  sulphate  of  copper,  to  which,  if  caustic  potash  be 
added,  blue  liquids  are  obtained,  and  these  being  heated, 
the  grape  sugar  throws  down  a  green  precipitate,  which 
turns  deep  red,  the  solution  being  left  colorless  :  the  cane 
sugar  alters  very  slowly,  a  red  precipitate  gradually  form- 
ing, and  the  liquid  remaining  blue.  Grape  sugar,  like 
cane  sugar,  gives  with  common  salt  a  crystallized  com- 
pound. When  heated  to  212°  F.  it  loses  two  atoms  of 
water,  and  becomes  C^H^O^.- 

Milk  Sugar — Lactine  (C12jri2Ol2) — ;may  be  obtained 
by  evaporating  whey  to  a  sirup,  and  the  crystals  which 
then  form  are  to  be  purified  by  animal  charcoal.  It  is 
sparingly  soluble,  requiring  five  or  six  times  its  weight  of 
water.  The  crystals  are  gritty^  between  the  teeth.  It  is 
through  the  alcoholic  fermentation  of  this  body  that  the 
Tartars  procure  intoxicating  milk. 

Besides  the  foregoing,  there  are  several  subordinate 
varieties  of  sugar,  among  which  may  be  cited 

Ergot  sugar *    .    .  C^H^O^ ; 

Eucalyptus  sugar     ......  CuHuOu; 

and  others,  as  liquorice  sugar,  mushroom  sugar,  or  man- 
nite,  &c. 

GrUM . — Gum  Arabic  is  obtained  from  several  species  of 
the  mimosa  or  acacia,  from  the  bark  of  which  it  exudes ; 
is  obtained  in  white  or  yellowish  tears,  of  a  vitreous  as- 
pect. It  dissolves  in  cold  water,  forming  mucilage,  from 
which  it  may  be  precipitated  pure,  as  Arabine,  by  alcohol. 

Bassorine  is  the  principle  of  Gum  Tragacanth ;  it  does 
not  dissolve  in  water,  but  merely  forms  a  jelly-like. mass. 
With  this  substance  should  be  classed  Pectine,  the  jelly 
obtained  from  currants  and  other  fruits.  This  substance 
furnishes  Pectic  acid  by  the  action  of  bases. 

What  is  the  difference  between  cane  and  grape  sugar  ?  By  what  test 
may  they  be  distinguished?  What  are  the  properties  of  milk  sugar? 
Mention  some  other  varieties  of  sugar.  From  what  source  is  gum  de- 
rived ?  What  are  arabine,  bassorine,  and  pectine  ? 


LIGNINE.  #15 

LIGNINE. — This  substance,  with  Cellulose  and  other  bod- 
ies, forms  the  woody  fibre  or  ligneous  tissue  of  plants.  It 
occurs  in  a  state  of  purity  in  the  fibres  of  fine  linen  and 
cotton,  and,  as  is  well  known,  is  of  perfect  whiteness,  in- 
soluble in  water  and  alcohol,  and  tasteless.  Strong  and 
cold  sulphuric  acid  converts  it  into  a  dextrine,  as  may  be 
shown  by  adding  to  that  substance  pieces  oJf  linen,  taking 
care  that  the  temperature  does  not  rise  ^so  as  to  blacken 
the  mixture,  which  is  to  be  well  stirred,  and  suffered  to 
stand  for  a  time.  On  dissolving  it  then  in  water,  and 
neutralizing  by  the  addition  of  chalk,  dextrine  is  obtained  ; 
or  if,  before  neutralizing,  the  solution  is  well  boiled,  grape 
sugar  is  produced. 


LECTURE  LXIX. 

ACTION  OF  AGENTS  ON  THE  STARCH  GROUP. — Action  of 
Sulphuric  Acid  on  Sugar.  —  Glucic  Acid  produced  by 
Lime. — Melassic  Acid. — Action  of  Nitric  Acid. — Pro- 
duction of  Oxalic  Acid. — Constitution  of  Oxalic  Acid. — 
Its  Salts.  —  Oxamide. — Saccharic  Acid.  —  Rhodizonic 
and  Croconic  Acids.  —  Mucic  Acid.  —  Xyloidine. — Its 
Properties, 

IN  the  preceding  Lecture  we  have  already  explained 
the  change  of  starch  into  sugar,  and  of  lignine  into  dex- 
trine, under  the  influence  of  sulphuric  acid  ;  and  in  the 
vegetable  world  there  can  be  no  doubt  that  these  and 
other  similar  modifications  arise  from  the  action  of  many 
causes.  On  inspecting  the  constitution  of  the  group,  it 
will  be  seen  that,  in  theory,  this  is  to  be  done  by  the  ad- 
dition or  abstraction  of  water. 

When  melted  grape  sugar  is  mixed  with  strong  sul- 
phuric acid,  and  the  diluted  solution  neutralized  with  car- 
bonate of  baryta,  the  sulphosaccharate  of  baryta  is  found 
in  the  solution.  The  Sulphosaccharic  acid  is  a  sweetish 
liquid,  readily  decomposing  into  sugar  and  sulphuric  acid. 

When,  in  the  process  of  converting  cane  sugar  into 

How  may  lignine  be  prepared?  When  pure,  what  is  its  color,  and 
what  its  relation  to  water  ?  How  may  it  be  converted  into  dextrine  and 
grape  sugar  ?  In  this  change,  what  is  the  action  impressed  on  the  lignine  ? 
How  is  sulphosaccharic  acid  made  ? 


315  OXALIC    ACID. 

grape  sugar  by  boiling  with  sulphuric  acid,  the  action  is 
long  continued,  a  dark-colored  substance  is  formed,  con- 
sisting of  two  different  bodies,  Ulmine  and  Ulmic  Acid,  or, 
as  they  are  termed  by  Liebig,  Sacchulmine  and  Sacchulmic 
Acid.  The  latter  is  converted  into  the  former  by  contin- 
ued boiling  in  water. 

When  a  solution  of  grape  sugar  containing  lime  is  kept 
for  some  time,  the  alkaline  reaction  of  the  lime  finally 
disappears  through  the  formation  of  Glucic  Acid,  the  con- 
stitution of  which  is  C&HhOb.  It  is  soluble,  deliquescent, 
of  a  sour  taste,  and  yielding,  for  the  most  part,  soluble 
salts.  If  grape  sugar  be  boiled  with  potash  water  until  it 
becomes  black,  a  dark  substance  may  be  precipitated  by 
an  acid.  This  is  Melasinic  Acid,  its  constitution  being 

CwJSeCk 

These  are  some  of  the  less  important  results  of  the 
action  of  acid  and  alkaline  bodies  on  the  starch  group  ; 
there  are  others  of  far  more  interest. 

OXALIC  ACID  (C2O3,  HO -\-2Aq). — Oxalic  acid  is  formed 
by  the  action  of  nitric  acid  on  starch  or  sugar,  or  any  other 
of  the  starch  group,  except  gum  and  sugar  of  milk.  One 
part  of  sugar  is  to  be  mixed  with  five  of  nitric  acid,  di- 
luted with  twice  its  weight  of  water,  and  the  acid  finally 
distilled  off  until  the  residue  will  deposit  crystals  on  cool- 
ing. These,  being  collected,  are  to  be  purified  by  redis- 
solving  and  crystallizing.  They  are  oblique  rhombic 
prisms,  more  soluble  in  liot  than  cold  water,  of  an  in- 
tensely acid  taste,  and  poisonous  to  the  animal  economy, 
chalk  or  magnesia  being  the  antidote.  Oxalic  acid  also 
occurs  naturally  in  several  plants,  in  union  with  potash 
or  lime. 

As  the  foregoing  formula  shows,  the  crystals  of  oxalic 
acid  contain  one  equivalent  of  saline  water  and  two  of 
water  of  crystallization.  The  latter  may  be  removed  by 
exposure  to  a  low  heat,  the  crystals  then  becoming  a 
white  powder,  and  subliming  without  difficulty.  Any  at- 
tempt to  remove  the  saline  water  and  isolate  the  oxalic 
acid  (as  C3O3)  leads  to  its  decomposition.  Thus,  when 
the  acid  is  heated  with  oil  of  vitriol,  total  decomposition 

What  are  sacchulmine  and sacchulmic  acid?  What  is  the  constitution 
of  glucic  acid  ?  What  is  the  action  of  potash  on  grape  sugar  ?  Describe 
the  preparation  of  oxalic  acid.  What  is  the  antidote  to  it  ?  What  is 
the  action  of  oil  of  vitriol  on  oxalic  acid  ? 


BALTS    OF    OXALIC    ACID.  317 

results  ;  equal  volumes  of  carbonic  oxide  and  carbonic 
acid  are  set  free  :  for  the  constitution  of  oxalic  acid  is 
such,  that  we  may  regard  it  as  composed  of  an  atom  of 
each  of  those  bodies  : 

C,03...  =  ...COa  +  CO; 

and  upon  this  is  founded  one  of  the  methods  of  preparing 
carbonic  oxide  gas.  The  gaseous  mixture  which  results 
from  the  action  of  the  oil  of  vitriol  is  passed,  as  in  Fig. 
243,  through  a  bottle  containing  potash  water,  which  ab- 
sorbs the  carbonic  acid,  and  the  carbonic  oxide  may  be 
collected  at  the  water  trough. 

The  production  of  oxalic  acid  from  sugar  by  nitric  acid 
is  due  to  the  replacement  of  hydrogen  by  an  equivalent 
quantity  of  oxygen. 

C12H909  ..  +  018...  =  ...  C12018 . .  +  H909 ; 
that  is,  one  atom  of  dry  sugar  with  eighteen  of  oxygen 
yields  six  atoms  of  oxalic  acid  and  nine  of  water. 

Salts  of  Oxalic  Acid. 

There  are  three  potash  salts  :  1st.  Neutral  Oxalate  of 
Potash,  made  by  neutralizing  oxalic  acid  with  carbonate 
of  potash  ;  crystallizes  in  rhombic  prisms,  soluble  in  three 
times  its  weight  of  water.  2d.  Binoxalate  of  Potash,  made 
by  dividing  a  solution  of  oxalic  acid  into  two  parts  ;  neu- 
tralize one  with  carbonate  of  potash,  and  then  add  the 
other.  It  crystallizes  in  rhombic  prisms,  has  a  sour  taste, 
and  dissolves  in  forty  parts  of  water.  It  occurs  naturally  in 
several  plants,  as  the  Oxalis  Acetosella.  3d.  Quadroxalate 
of  Potash.  Divide  a  solution  of  oxalic  acid  into  four  parts  ; 
neutralize  one  and  add  the  rest.  It  crystallizes  in  octa- 
hedrons ;  less  soluble  than  either  of  the  foregoing.  These 
salts  are  sometimes  used  for  the  removal  of  ink  stains 
from  linen. 

Oxalate  of  Ammonia,  prepared  by  neutralizing  a  hot 
solution  of  oxalic  acid  with  carbonate  of  ammonia.  It  crys- 
tallizes in  rhombic  prisms,  which  are  efflorescent.  Its  so- 
lution is  used,  as  has  been  already  stated,  as  a  test  and 
precipitant  of  lime.  When  exposed  to  heat  in  a  retort,  it 
is,  for  the  most  part,  decomposed  into  water,  ammonia, 

How  is  this  acid  produced  from  sugar  ?  How  many  oxalates  of  potash 
are  there  ?  How  are  they  prepared  ?  For  what  purpose  are  these  salt* 
sometimes  used  ? 

DD2 


318  SACCHARIC MUCIC    ACIDS. 

carbonic  acid,  cyanogen,  and  other  compounds ;  but  a  sub- 
stance of  the  name  of  Oxamide  also  sublimes,  the  consti- 
tution of  which  is 

C&  NO,..  .  =  ...NH2  +  2(CO), 

that  is,  containing  the  constituents  of  one  atom  of  amido- 
gen  and  two  of  carbonic  oxide.  This  remarkable  sub- 
stance, when  boiled  with  potash,  yields,  through  the  de- 
composition of  water,  oxalate  of  potash  and  ammoniacal 
gas. 

Oxalate  of  Lime  occurs  naturally,  forming  the  skeleton 
of  many  lichens,  and  is  obtained,  as  has  just  been  said,  by 
precipitating  a  lime  salt.  It  is  soluble  in  nitric  acid,  and, 
ignited  in  a  covered  crucible,  is  converted  into  carbonate 
of  lime. 

SACCHARIC  ACID  (C^H^On  +  dlfO) — Oxalhydric  Acid, 
— -made  by  the  action  of  dilute  nitric  acid  on  sugar.  It  is 
a  pentabasic  acid. 

RHODIZONIC  ACID  (C7O7-\-3HO),  obtained  by  the  action 
of  potassium  on  carbonic  oxide  at  a  red  heat.  When 
boiled,  it  changes  into  Croconic  Acid,  a  yellow  body  hav- 
ing the  constitution  C5O4-\-HO. 

MUCIC  ACID  (CuHaO4+2HO),  obtained  by  the  action 
of  dilute  nitric  acid  on  gum  or  sugar  of  milk,  as  in  the 
preparation  of  oxalic  acid  by  other  members  of  the  starch 
group.  It  requires  sixty  times  its  weight  of  water  for  so- 
lution. Decomposed  by  heat,  it  yields  pyromucic  acid. 

XYLOIDINE  (C6H4O4,  NOb\  made  by  the  action  of  nitric 
'acid,  sp.  gr.  1*5,  on  starch,  which  is  converted  into  a  gelati- 
nous body,  and  yields  this  substance  as  a  white  precipi- 
tate when  acted  on  by  water.  Its  origin  is  apparent  from 
a  comparison  of  its  formula  with  that  of  starch.  Xyloid- 
ine  is  insoluble  in  boiling  water,  but  by  the  continued  ac- 
tion of  nitric  acid  changes  into  oxalic  acid.  100  parts  of 
starch  yield  128  of  xyloidine. 

GUN  COTTON. — Pyroxyline.  A  remarkable  compound, 
proposed  as  a  substitute  for  gunpowder  by  Schonbein, 
whose  process  for  preparing  it  has  not  yet  been  divulged. 
It  may  be  made  by  the  action  of  monohydrated  nitric  acid 

Under  what  circumstances  does  oxamide  form?  What  is  its  constitu- 
tion? How  is  saccharic  acid  made?  Under  what  circumstances  can 
glass  be  silvered  with  it?  How  is  the  rhodizonate  of  potash  formed? 
What  is  its  composition  ?  How  is  it  changed  into  croconic  acid  ?  Under 
what  circumstances  does  mucic  acid  form  ? 


FERMENTATION.  319 

on  cotton,  paper,  or  sawdust;  and  still  more  conveniently  by 
a  mixture  of  nitric  and  sulphuric  acids  on  those  substances. 
The  cheapest  and  best  process  for  its  preparation  is  that 
discovered  by  Prof.  Ellet,  of  South  Carolina  College.  It 
consists  in  soaking  carded  cotton  for  a  few  minutes  in  a 
mixture  of  pulverized  nitrate  of  potash  and  oil  of  vitriol, 
washing  the  result  in  hot  water  to  free  the  cotton  from 
the  potash  salt,  and  finishing  the  washing  by  a  weak  so- 
lution of  ammonia.  Gun  cotton  appears  white,  like  or- 
dinary cotton,  the  fibre  being  little  changed ;  it  is  some- 
what harsh  to  the  touch  ;  when  perfectly  dry,  it  explodes 
when  heated  to  about  300  F.,  or  by  the  blow  of  a  ham- 
mer. It  is  estimated  as  having  about  three  times  the  me- 
chanical force  of  gunpowder.  100  parts  of  cotton  yield 
about  165  of  gun  cotton.  It  contains  twice  as  much  nitric 
acid  as  xyloidine. 


LECTURE  LXX. 

ON  THE  METAMORPHOSIS  OF  THE  STARCH  GROUP  BY  Ni- 
TROGENIZED  FERMENTS. — Action  of  Leaven. — Bread. — 
Fermentation  of  Sugar. — Fermentation  of  Grape  Juice. — 
Primary  Action  on  the  Ferment. — Activity  of  Ferments 
due  to  Nitrogen. — Effects  of  Temperature. — Production  oj 
Butyric  Acid. — Ferments  of  different  Properties. — Pro- 
duction of  Wine  and  intoxicating  Liquids. 

IN  the  preceding  Lecture  we  have  traced  the  action 
of  the  more  powerful  inorganic  agents  on  the  amyles,  and 
seen  how  a  variety  of  bodies  of  different  characters  arise, 
some  of  which,  as  oxalic  acid,  are  of  very  considerable 
importance. 

But  there  is  another  system  of  changes  which  can  be 
impressed  on  this  group  of  bodies,  far  more  curious  in  its 
nature,  and  leading  to  far  more  important  results. 

When  flour,  made  into  a  paste  with  water,  is  brought 
in  contact  with  Leaven,  that  is  to  say,  a  similar  dough,  un- 
dergoing an  incipient  putrefactive  fermentation,  at  a  tem- 
perature of  60°  or  70°  F.,  bubbles  of  gas  are  disengaged, 

Decomposed  by  heat,  what  does  mucic  acid  yield  ?  How  is  xyloidine 
prepared,  and  what  are  its  properties  ?  What  is  the  action  of  leaven  on 


320  ACTION    OF    FERMENTS. 

the  paste  swells  up,  and,  when  baked,  forms  leavened 
bread.  This  ancient  process,  which  is  now  in  use  all  over 
the  world,  depends  on  the  action  of  the  changing  leaven 
being  propagated  to  the  sugar  which  the  flour  contains. 
The  sugar  is  resolved  into  alcohol  and  carbonic  acid  gas, 
the  former  of  which  may  be  obtained  by  distilling  the 
dough  j  and  the  bubbles  of  the  latter,  entrapped  in  the 
yielding  mass,  gives  to  the  bread  the  lightness  for  which 
it  is  prized. 

But  this  process  may  be  better  traced  by  observing 
the  phenomena  of  alcoholic  fermentation  in  the  case  of 
pure  sugar.  If  we  take  a  solution  of  sugar  in  water,  it 
may  be  kept  for  a  length  of  time  without  undergoing  any 
change  ;  but  if  nitrogenized  matters,  such  as  blood,  albu- 
men, leaven,  in  a  state  of  putrescent  decay,  are  mixed 
with  it,  then,  at  a  temperature  of  70°  F.,  the  sugar  rapidly 
disappears,  carbonic  acid  is  given  off,  and  alcohol  is  found 
in  the  solution.  The  change  is  obvious. 

'  ClzHl2Ou ...  =  ... 2(C<HQ0.2)  +  4(C02) ; 

that  is,  one  atom  of  dry  grape  sugar  yields  two  of  alco- 
hol and  four  of  carbonic  acid.  The  final  action,  there- 
fore, of  the  ferment  is  to  split  the  sugar  atom  into  carbon- 
ic acid  and  alcohol. 

Of  all  ferments,  Yeast,  for  these  purposes,  is  the  most 
powerful ;  it  is  a  substance  which  arises  during  the  fer- 
mentation of  beer.  It  is  probable  that,  in  the  various 
sugars,  the  first  action  is  to  bring  them  into  the  condition 
of  grape  sugar,  and  then  the  metamorphosis  ensues. 

By  an  analogous  transformation  of  the  sugar  contained 
in  fruits,  the  different  wines  and  other  intoxicating  liquids 
are  formed  ;  thus,  if  we  take  the  expressed  juice  of  grapes 
which  has  not  been  exposed  to  the  contact  of  air,  it  may 
be  kept  for  a  length  of  time  without  change  ;  but  if  a  sin- 
gle bubble  of  oxygen  is  admitted  to  it,  fermentation  at 
once  sets  in,  the  grape  .  sugar  disappears,  and  alcohol 
comes  in  its  stead,  carbonic  acid  gas  being  disengaged, 
and  the  nitrogenized  substance,  yeast,  deposited.  If  a  so- 
lution of  pure  sugar  be  added,  it  is  involved  in  the  change, 
and  portion  after  portion  will  disappear  ^  but,  finally,  the 

What  is  the  action  of  decaying  nitrogenized  matter  on  a  solution  of  sugar  ? 
Into  what  bodies  does  the  sugar  atom  split?  What  is  the  action  of  yeast 
on  sugar  ?  Describe  the  action  of  yeast  on  grape  juice> 


ACTION    OF    FERMENTS.  321 

yeast  itself  is  exhausted,  and  then  any  excess  of  sugar  re- 
mains unacted  upon. 

It  is  obvious  that  the  primary  action  is  an  oxydation 
of  the  ferment,  and  the  moment  its  particles  are  set  in 
motion  the  motion  is  propagated  to  the  adjacent  body, 
the  particles  of  which  submit  in  succession  ;  and  there- 
fore the  fermentation  is  not  a  sudden  action,  but  one  re- 
quiring time.  Moreover,  it  is  plain  that  the  action  is  lim- 
ited ;  a  given  quantity  of  yeast  will  transmute  only  a  defi- 
nite quantity  of  sugar. 

The  ferments,  or  bodies  which  possess  this  singular 
quality,  are  nitrogenized  bodies ;  and,  inasmuch  as  non- 
nitrogenized  bodies  never  •  spontaneously  ferment  while 
oxydizing,  it  is  to  the  nitrogen  that  we  are  to  impute  the 
qualities  in  question. 

Temperature  has  a  remarkable  control  over  ferment 
action.  The  juice  of  carrots  or  beets,  fermenting  at  50° 
Fahr.,  will  yield  alcohol,  carbonic  acid,  and  yeast;  but 
the  same  juices,  fermenting  at  120°  Fahr.,  produce  lactic 
acid,  gum,  and  mannite.  Under  these  circumstances, 
therefore,  alcohol  is  the  product  of  fermentation  at  low, 
and  lactic  acid  at  high  temperatures. 

But  when  milk  ferments  at  50°  Fahr.,  lactic  acid  is  the 
chief  product,  while  at  80°  Fahr.  the  casein  acts  like  a 
yeast  ferment,  the  milk  sugar  becoming  transformed  into 
grape  sugar,  and  then  resolving  itself  into  alcohol  and 
carbonic  acid.  In  this  instance  the  action  is  the  reverse 
of  the  former,  lactic  acid  being  the  product  of  a  low,  and. 
alcohol  of  a  high  temperature. 

A  very  remarkable  decomposition  takes  place  when 
casein  ferment  acts  on  sugar  at  80°  Fahr.  in  presence  of 
carbonate  of  lime.  Under  these  circumstances,  carbonic 
acid  gas  and  hydrogen  are  evolved,  and  Butyric  Acid  ap- 
pears. On  comparing  the  constitution  of  butyric  acid 
with  alcohol,  it  will  be  seen  that  the  latter  contains  the 
elements  of  the  former,  with  an  excess  of  hydrogen  ;  so 
that,  during  this  fermentation,  the  alcohol  atom  is  divided. 

All  ferments  possess  certain  properties  in  common,  but 
each  has  its  specific  powers  ;  and  the  products  which  are 

What  is  the  primary  action  in  these  cases  ?  Is  the  action  of  the  fer- 
ment definite  ?  To  what  element  in  the  yeast  is  the  action  due  1  What 
is  the  effect  of  temperature  on  fermentation?  Describe  the  causes  of  the 
fermentation  of  vegetable  juices  and  of  milk  ?  Under  what  circumstances 
does  butyric  acid  form  ? 


322  PREPARATION    OP    WINES. 

evolved  differ  in  different  cases.  Most  commonly  the  ac- 
tivity of  these  bodies  is  excited  by  an  incipient  oxyda- 
tion,  the  result  of  whkh  would  be  to  bring  the  ferment 
itself  to  a  simpler  constitution.  In  this  respect,  therefore, 
the  first  stage  of  fermentation  is  a  combustion  at  common 
temperatures,  or  an  eremacausis  of  the  ferment  itself; 
but  this  action  is  speedily  propagated  to  the  surrounding 
mass,  which  becomes  involved  in  the  change.  What- 
ever, therefore,  prevents  the  incipient  oxydation  of  the 
ferment  puts  a  stop  to  the  whole  process.  By  raising 
their  temperature  to  212°,  and  then  cutting  off  the  access 
of  air,  substances  which  would  otherwise  undergo  a  very 
rapid  change  may  be  kept  for  any  length  of  time  without 
alteration.  On  this  principle,  meats,  milk,  and  other  viands 
may  be  preserved. 

We  have  now  pointed  out  the  peculiarities  of  ferment 
action,  showing  that  two  successive  stages  may  be  traced 
in  the  process ;  the  first  arising  in  the  oxydation  of  the 
ferment,  by  which  its  molecules  are  decomposed ;  and  the 
second,  which  consists  in  the  propagation  of  this  move- 
ment to  the  surrounding  particles,  upon  which  changes 
are  impressed,  the  nature  of  which  differs  with  the  tem- 
perature and  the  specific  action  of  the  ferment  itself. 

Wine  is  made  from  the  expressed  juice  of  grapes,  which, 
containing  a  nitrogenized  body,  albumen,  when  exposed 
to  the  air  undergoes  spontaneous  fermentation  ;  the  course 
of  the  action  being,  1st.  The  oxydation  of  the  vegetable 
albumen ;  2d.  The  propagation  of  its  action  to  the  grape 
sugar.  If  the  sugar  is  in  excess,  the  wine  remains  sweet ; 
if  the  albumen  is  in  excess,  the  wine  is  dry.  The  vrine, 
as  soon  as  the  first  action  is  over,  is  removed  into  casks. 
During  these  changes,  the  bitartrate  of  potash,  which 
exists  naturally  in  grape  juice,  and  which,  though  sparing- 
ly soluble  in  water,  is  much  less  so  in  alcohol,  is  deposit- 
ed. It  goes  under  the  name  of  Argol.  Most  other  fruit 
juices  contain  free  acid,  such  as  malic  or  citric  ;  and  hence 
good  wine  can  not  be  made  from  them,  because,  if  all  the 
sugar  is  removed,  they  possess  a  sharp  taste  ;  and  if,  as  is 

What  is  the  change  which  the  ferment  itself  undergoes  ?  What  is  the 
effect  of  cutting  off  the  access  of  air  ?  What  are  the  two  stages  of  fer- 
ment action  ?  What  is  the  process  for  the  making  of  wine  ?  When  is  the 
wine  sweet,  and  when  dry  ?  What*s  argol  ?  Why  are  other  fruit  juice* 
less  proper  for  making  wine  than  grape  juice  ? 


ALCOHOL.  323 

commonly  the  case,  a  portion  is  left  to  correct  the  acid- 
ity, it  is  liable  to  run  into  a  second  fermentation. 

Inferior  liquids,  such  as  cider,  perry,  &c.,  are  made 
from  other  vegetable  juices,  as  those  of  apples,  pears,  &c. 
Beer,  porter,  and  ale  are  made  from  an  infusion  of  malt, 
which  is  barley,  a  portion  of  the  starch  of  which  is  trans- 
posed into  sugar  by  partial  germination.  The  principles 
of  the  fermentation  are,  in  all  these  instances,  the  same. 


LECTURE  LXXJ. 

ON  THE  DERIVATIVES   OF  FERMENTATIVE  PROCESSES.- 

Alpohol. — Its  Properties. — Exists  in  Wines. — Lactic 
Add. — Production  and  Properties. — Sulphuric  Ether. 
— Its  Distillation. —  The  Ethyh  Series. — Chloride. — 
Bromide.-r-Nitrate,  fyc. — CEnanthic  Ether. 

ALCOHOL  (Hydrated  Oxide  of  E thy k)  CAH6O2. 

BY  the  distillation  of  wine,  or  any  other  fermented  sac- 
charine juice,  spirits  of  wine  maybe  obtained.  As  first  pre- 
pared, it  contains  a  large  quantity  of  water,  which  comes 
over  with  it.  This  product  being  rectified,  and  the  first  por- 
tion preserved,  yields  a  spirit  containing  twelve  to  fifteen 
per  cent,  of  water.  By  putting  this  into  a  retort  with  half 
its  weight  of  quicklime,  keeping  the  mixture  a  few  days, 
and  then  distilling  at  'a  low  temperature,  absolute  or  an- 
hydrous alcohol  is  obtained. 

Anhydrous  alcohol  is  a  colorless  liquid  of  .a  burning 
taste  and  pleasant  odor.  Its  specific  gravity,  at  60°  F.,  is 
0-795.  It  boils  at  123°  F.,  and  at  a  still  lower  point  if  slight- 
ly diluted  with  water,  though  the  boiling  point  rises  if  the 
water  be  in  greater  proportion.  It  has  not  been  yet  fro- 
zen. The  specific  gravity,  also,  varies  with  the  amount  of 
water  present;  and  hence  the  purity  of  spirits  of  wine 
may  be  determined  by  ascertaining  its  density.  Alcohol 
is  very  inflammable,  burns  with  a  pale  blue  flame,  with 
the  producton  of  carbonic  acid  gas  and  water.  It  is  much 
used  in  chemical  investigations  as  furnishing  a  lamp  flame 
free  from  smoke,  and  as  possessing  an  extensive  range  of 

How  is  alcohol  procured  ?  How  may  it  be  obtained  anhydrous  ?  What 
are  its  properties  1  How  may  the  strength  of  spirits  of  wine  be  deter- 
mined ?  For  what  purposes  is  it  used  in  chemistry  ? 


324  LACTIC    ACID. 

solvent  powers,  acting  upon  resins,  oils,  and  other  bodies, 
which  are  not  acted  upon  by  water. 

The  strong  wines,  such  as  port  and  sherry,  contain  from 
nineteen  to  twenty-five  per  cent,  of  alcohol ;  the  light 
wines  from  twelve  per  cent,  upward ;  and  beer,  porter, 
&c.,  from  five  to  ten  per  cent. 

Lactic  Acid  Fermentation. — We  have  already  seen  that 
vegetable  juices  as  well  as  milk  will,  under  certain  cir- 
cumstances of  temperature,  yield,  during  fermentation, 
lactic  acid  instead  of  alcohol.  This  acid  may,  therefore, 
be  made  by  dissolving  a  quantity  of  sugar  of  milk  in  milk, 
putting  it  in  a  warm  place,  and  allowing  it  to  turn  sour 
spontaneously.  A  part  of  the  caseine  of  the  milk  here  acts 
as  the  ferment,  and  as  lactic  acid  is  set  free,  it  coagulates 
the  rest  and  makes  it  insoluble.  By  the  addition  of  car- 
bonate of  soda,  to  neutralize  the  acid,  this  is  prevented,  and 
the  ferment  resuming  its  activity,  produces  more  lactic 
acid.  When,  by  this  process,  all  the  sugar  is  exhausted, 
the  liquid  is  boiled,  filtered,  evaporated  to  dryness,  and 
the  lactate  of  soda  dissolved  out  by  hot  alcohol.  From 
this  alcoholic  solution  the  acid  may  be  obtained  by  pre- 
cipitating the  soda  by  sulphuric  acid. 

Lactic  Acid  ( C6H5Or,-\-HO)  is  obtained  as  a  sirupy  solu- 
tion by  concentrating  in  a  vacuum  over  oil  of  vitriol.  It  is 
colorless,  has  a  specific  gravity  of  1'215,  is  very  sour,  and 
soluble  in  water  and  alcohol.  It  yields  a  complete  series 
of  salts,  most  of  which  are  soluble.  Among  these  salts, 
the  most  interesting  are  those  of  lime  and  of  zinc. 

ETHER — Sulphuric  Ether — Oxide  of  Ethyle  (C4H5O). 
— Ether  is  prepared  by  distilling  equal  weights  of  alcohol 
and  oil  of  vitriol,  receiving  the  resulting  vapor  in  a  Lie- 
big's  condenser,  a  d  Ti  c,  as  in  Fig.  269,  the  condenser  be- 
ing cooled  by  water  from  the  reservoir,  ?',  flowing  into  the 
funnel,  c,  the  waste  passing  into  the  vessel,  b,  and  the  ether 
distilling  into  the  bottle,  e.  The  process  is  to  be  stopped 
as  soon  as  the  mixture  begins  to  blacken.  The  first  prod- 
uct may  be  rectified  by  redistillation  from  caustic  potash. 
'"  Ether  is  a  colorless  and  limpid  liquid,  of  a  peculiai 
odor  and  hot  taste.  It  boils  at  t)6°  F.,  and  has  not  yet 

How  much  alcohol  per  cent,  is  contained  in  port,  sherry,  beer  and  ale  ? 
What  is  the  process  for  obtaining  lactic  acid  ?  What  is  its  constitution  ? 
What  are  its  properties  ?  How  is  ether  made  ?  What  are  the  proper- 
ties of  ether? 


COMPOUNDS    OF    ETHYLE. 


325 


been  frozen.  Its  specific  gravity,  at  60°  F.,  is  -720.  It 
volatilizes  with  rapidity,  and  therefore  produces  cold.  It 
is  combustible,  and  burns  with  the  evolution  of  much  more 
light  than  alcohol.  The  specific  gravity  of  its  vapor  is 
2-5S6.  With  oxygen  or  atmospheric  air  it  forms  an  ex- 
plosive mixture,  and,  kept  in  contact  with  air,  it  becomes 
acid  from  the  production  of  acetic  acid.  It  dissolves  in 
alcohol  in  all  proportions,  but  ten  parts  of  water  are  re- 
quired to  dissolve  one  of  it ;  it  also  dissolves  many  fatty 
substances,  and  hence  is  of  considerable  use  in  organic 
chemistry. 

Ether  is  regarded  as  the  oxide  of  an  ideal  compound 
radical,  ethyle,  C4H6,  which  gives  rise  to  a  series  of  othei 
bodies.  • 

The  Ethyle  Group. 

Ethyle,  C*H-0 =  Ae. 

Oxide  of  ethyle =  Ae,  O. 

Hydrated  oxide =  Ae,  O  +  HO. 

Chloride  of  ethyle =  Ae,  Cl. 

Bromide          " =  Ae,  B. 

Nitrate  "      .     :    . '  .     .  =  Ae,  O  4-  NOn. 

Hyponitrite     " =  Ae,  O  -j-  NOs. 

&c.  &c. 

The  oxide  of  ethyle,  as  has  just  been  stated,  is  ether  it- 
self. The  hydrated  oxide  is  alcohol. 

Is  it  soluble  in  water  ?  What  class  of  bodies  does  it  dissolve  ?  Of 
what  substance  is  it  an  oxide  ? 

E  E 


326  COMPOUNDS    OP   ETHYLE. 

Chloride  ofEthyle — Hydrochloric  Ether — may  be  made 
by  saturating  rectified  spirits  of  wine  with  dry  hydro- 
chloric acid  gas,  and  distilling  the  result  at  a  low  tempera- 
ture, conducting  the  vapor  through  a  bottle  of  warm  Wa- 
ter, and  then  condensing  in  a  receiver  surrounded  by  a 
freezing  mixture.  It  is  a  colorless,  volatile  liquid,  of  a 
peculiar  aromatic  smell ;  the  specific  gravity  is  '874.  It 
boils  at  52°,  and  is  not  decomposed  by  nitrate  of  silver. 

Bromide  of  Ethyle  (Hydrobromic  Ether)  and  Iodide  vf 
Ethyl  (Hydriodic  Ether)  are  not  of  any  importance  ;  and 
the  same  remark  may  be  made  as  respects  the  sulphuret 
and  the  cyanide. 

Nitrate  of  Ethyle — Nitric  Ether — may  be  made  on  the 
small  scale  by  distilling  equal  weights  of  alcohol  and  nitric 
acid  with  a.  small  quantity  of  nitrate  of  urea.  The  latter 
substance  is  used  to  prevent  the  nitric  acid  deoxydizing, 
and  giving  rise  to  the  production  of  hypoiiitrite  instead  of 
nitrate  of  ethyle.  Nitrate  of  ethyle  is  insoluble  in  water, 
has  a  density  of  1*112,  boils  at  185°,  and  has  a  sweet 
taste.  Its  vapor  explodes  when  heated. 

Hyponitrite  of  Ethyle — Nitrous  Ether  (AcO,  iVOa).— 
This  ether  may  be  made  by  passing  the  hyponitrous  acid, 
disengaged  from  one  part  of  starch  and  ten  of  nitric  acid, 
through  alcohol,  diluted  with  half  its  weight  of  water  and 
kept  cold.  It  is  a  yellowish,  aromatic  liquid,  having  the 
odor  of  apples.  It  boils  at  62°  F.  Its  density  is  '967. 
The  sweet  spirits  of  nitre  is  a  solution  of  this  ether  with 
aldehyde  and  other  substances  in  alcohol. 

Carbonate  of  Ethyle — Carbonic  Ether  (AeO,  CO2] — 
made  by  the  action  of  potassium  on  oxalic  ether,  and  distill- 
ation of  the  product  with  water.  It  floats  on  the  surface  of 
the  distilled  liquid,  is  an  aromatic  liquid,  and  boils  at  259°. 

Oxalate  ofEthyle — Oxalic  Ether — prepared  by  distill- 
ing four  parts  of  binoxalate  of  potash,  five  of  sulphuric 
acid,  and  four  of  alcohol  into  a  warm  receiver.  The 
product  is  washed  with  water  to  separate  any  alcohol 
or  acid,  and  redistilled.  It  is  an  oily  liquid,  of  an  aro- 
matic odor ;  it  boils  at  353°  F.,  and  is  slightly  heavier  than 
water.  With  an  excess  of  ammonia  it  yields  Oxamide  and 

What  is  the  true  name  of  hydrochloric  ether,  and  how  is  it  prepared  ? 
How  is  the  nitrate  of  ethyle  made  ?  How  is  nitrous  ether  prepared,  and 
what  are  its  properties  ?  How  are  carbonic  ether,  acetic  ether,  and  for- 
mic ether  made  ? 


SULPHOVINIC    ACID.  327 

alcohol.     With  a  smaller  proportion  of  ammonia  and  al- 
cohol it  yields  Oxamethane,  CSH7NOC. 

Acetate  of  Ethyle — Acetic  Ether  (AeO,  C4H3O^ — and 
Formiate  of  Ethyle — Formic  Ether  (AeO,  C.2HO^) — are 
procured  in  a  similar  manner  with  the  foregoing,  substi- 
tuting in  one  case  acetate  of  potash,  and  in  the  other 
formiate  of  soda. 

(Enanthic  Ether  (AeO,  C14JJ13O.2)  is  prepared  from  an 
oily  liquid  which  passes  over  during  the  distillation  of  cer- 
tain wines.  It  has  a  powerful  vinous  odor,  is  a  colorless 
liquid,  specific  gravity  -862  ;  it  boils  at  410°  F.,  dissolves 
readily  in  alcohol,  and  gives  their  peculiar  aroma  to  the 
wines  in  which  it  is  found.  From  it  cenanthic  acid  may 
be  obtained  by  the  successive  action  of  potash  and  sul- 
phuric acid.  It  is  an  oily  body,  becoming  a  soft  solid  at 
550  F. 


LECTURE  LXXII. 

DERIVATIVE  BODIES  OF  ALCOHOL. — Sulphovinic  and  Phos- 
phovinic  Acids. — Products  of  Sulphovinic  Acid  at  Dif- 
ferent Boiling  Points. —  The  continuous  Ether  Process. 
—  The  continuous  Olejiant  Gas  Process.  —  Dutch  Li- 
quid.-^-Successive  Substitutions  of  Chlorine  in  it. — Heavy 
and  Light  Oil  of  Wine. — Sulphate  of  Carbyle  and  its 
derivative  Acids. 

SULPHOVINIC  Acid^Bisulphate  of  Ethyle  (C±H-0O .2SO3 
+  HO). — A  mixture  of  sulphuric  acid  with  an  equal  weight 
of  alcohol  is  to  be  heated  to  the  boiling  point,  and  then 
allowed  to  cool.  It  is  then  to  be  diluted  with  water  and 
neutralized  with  carbonate  of  baryta;  the  sulphate  of  ba- 
ryta subsides.  The  solution  is  then  filtered,  evaporated, 
and,  when  cold,  the  sulphovinate  of  baryta  crystallizes. 
From  this  the  Sulphovinic  acid  may  be  obtained  by  pre- 
cipitating the  baryta  with  dilute  sulphuric  acid,  and  evap- 
orating the  resulting  solution  in  vacuo.  It  is  a  sirupy 
liquid,  of  a  sour  taste,  giving  rise  to  a  series  of  soluble 
salts,  which  decompose  at  the  boiling  point,  as  will  be  pres- 
ently seen. 

From  what  source  is  cenanthic  ether  derived  ?  What  is  its  relation  to 
vinous  bodies  ?  How  is  Sulphovinic  acid  made  ?  W  hat  is  its  composition  ? 


528  CONTINUOUS    ETHER    PROCESS. 

Phosphovinic  Acid  (CtH-aO,  PO5+2HO)  is  made  on  the 
same  principles  as  the  foregoing,  phosphoric  acid  being 
substituted  for  sulphuric,  and  decomposing  the  resulting 
baryta  salt  in  the  same  way.  It  is  a  sirupy  liquid,  of  a 
sour  taste,  and  dissolves  in  water,  alcohol,  and  ether  very 
readily.  It  is  decomposed  by  heat. 

If  sulphovinic  acid  be  diluted  so  as  to  bring  its  boiling 
point  below  260°  F.,  it  is  resolved  at  that  temperature 
chiefly  into  sulphuric  acid  and  alcohol,  which  distills  over. 

If  the  boiling  point  is  from  260°  F.  to  310°  F.,  the  dis- 
tillation results  chiefly  in  the  production  of  hydrated  sul- 
phuric acid  and  ether. 

If,  by  the  addition  of  sulphuric  acid,  the  boiling  point 
is  carried  above  320°  F.,  the  action  is  more  complex,  but 
the  chief  product  which  passes  over  is  olefiant  gas. 

The  ordinary  method  of  preparing  ether  is,  therefore, 
obviously  very  disadvantageous,  because  it  is  only  within 
a  particular  range  of  temperature  that  that  body  is  evolved. 
At  first  the  low  temperature  yields  alcohol,  and  as  the 
heat  rises,  the  mixture  begins  to  blacken  and  olefiant  gas 
to  be  evolved. 

To  obviate  these  difficulties,  a  very  beautiful  process, 
the  continuous  process,  has  been  introduced.  It  consists 
in  taking  a  mixture  of  eight  parts  by  weight  of  sulphuric 
acid  and  five  of  alcohol,  specific  gravity  '834,  the  boiling 
point  of  which  is  about  300°  F.  This  is  brought  to  that 
temperature,  and  alcohol  of  the  same  density  is  allowed 
slowly  to  flow  into  the  mixture,  the  boiling  point  being 
steadily  kept  as  near  300°  F.  as  possible,  and  the  mixture 
maintained  in  a  state  of  violent  ebullition.  Water  and 
ether  distill  over  together,  and  may  be  passed  through  a 
Liebig's  condenser;  they  collect  in  the  receiver  in  sepa- 
rate strata,  or,  if  this  does  not  take  place  at  first,  the  ad- 
dition of  a  little  water  in  the  receiver  insures  it. 

In  this  manner  a  very  large  quantity  of  alcohol  maybe 
converted  into  ether  and  water  by  the  action  of  a  limited 
amount  of  sulphuric  acid  ;  and  in  a  similar  manner,  by  ad- 
justing the  boiling  point  so  as  to  be  between  320°  and 
330°  F.,  olefiant  gas  may  be  continuously  obtained.  All, 
therefore,  that  is  required,  is  to  convey  the  alcoholic  va- 

\Vhat  is  the  composition  and  mode  of  preparation  of  phosphovinic  acid  ? 
What  is  the  result  of  the  exposure  of  sulphovinic  acid  at  different  boiling 
points  ?  Describe  the  continuous  process  for  the  preparation  of  ether. 


SUBSTITUTIONS    IN    DUTCH    LIQUID.  329 

por  through  a  mixture  of  oil  of  vitriol  with  half  its  weight 
of  water,  which  has  the  required  boiling  point.  In  this 
process  the  acid  does  not  blacken,  and  it  is  therefore  much 
more  advantageous  than  that  described  for  the  preparation 
of  olefiant  gas  in  Lecture  LI V. 

Chloride  of  Olefiant  Gas — Dutch  Liquid  (C4H4C1.2)— 
is  prepared  by  mixing  equal  volumes  of  chlorine  and  ole- 
fiant gas  in  a  large  glass  globe.  It  is  a  colorless  and  fra- 
grant liquid,  soluble  in  alcohol  and  ether,  but  less  so  in 
water.  It  boils  at  180°  F.,  and  when  acted  on  by  a  so- 
lution of  caustic  potash  in  alcohol,  it  yields  chloride  of 
potassium  and  a  substance  C^H^Cl,  which,  on  being  cooled 
by  a  freezing  mixture,  condenses  into  a  liquid.  This  li- 
quid, brought  in  contact  with  chlorine,  absorbs  that  sub- 
stance, and  yields  a  new  compound,  C±HAClr  which  may 
again  be  decomposed  by  an  alcoholic  solution  of  potash 
into  chloride  of  potassium  and  a  new  volatile  body, 
C4H,C12. 

There  is  an  iodide  and  a  bromide  of  olefiant  gas,  which 
possess  a  constitution  analogous  to  the  chloride. 

When  chlorine  gas  is  made  to  act  upon  Dutch  liquid, 
three  different  substances  may  be  successively  formed  by 
the  gradual  abstraction  of  hydrogen,  and  its  equivalent 
substitution  by  chlorine.  These  substances  are  as  follow : 

Dutch  liquid  .......  C4H4C12. 

(1.) C4H3C13. 

(2.) C4H2Cl<. 

(3.) C4       CI&. 

The  first  and  second  of  these  products  are  volatile  li- 
quids, the  third  is  the  perchloride  of  carbon,  in  which  it  ap- 
pears that  all  the  four  atoms  of  hydrogen  in  the  Dutch 
liquid  have  been  removed,  and  their  places  occupied  by 
four  atoms  of  chlorine.  This  perchloride  of  carbon  is  a 
white,  crystalline  body,  soluble  in  alcohol  and  ether.  Its 
melting  point  is  320°  F.  By  passing  its  vapor  through  a 
red-hot  porcelain  tube,  it  is  decomposed,  yielding  C4C14, 
and  free  chlorine,  and  this  again  gives  rise  to  subchloride 
of  carbon,  C4C/2,  by  being  passed  through  an  ignited  por- 
celain tube  at  a  white  heat.  The  former  of  these  bodies 
is  a  colorless  liquid,  and  the  latter  a  silky  solid. 

Heavy  Oil  of  Wine  (C<H,O,  2SOS)  may  be  procured 

Describe  the  continuous  process  for  preparing  olefiant  gas.  How  is 
Dutch  liquid  prepared  ?  What  is  the  nature  of  the  series  of  bodies  arising 
from  the  action  of  chlorine  on  it  ? 

E  E2 


330  OXYDATION    OF    ALCOHOL. 

by  the  destructive  distillation  of  sulphovinate  of  lime,  or 
by  distilling  two  and  a  half  parts  of  oil  of  vitriol  and  one 
of  spirit  of  wine.  It  is  a  colorless  liquid,  heavier  than 
water,  and  having  an  odor  of  peppermint.  Boiled  with 
water,  it  yields  sulphovinic  acid,  and  Light,  or  Sweet  Oil 
of  Wine,  a  substance  which,  after  standing  a  few  days,  de- 
posits white  inodorous  crystals  of  Etherine,  C4H4.  The 
residue,  which  still  remains  liquid,  is  Etherole,  C4H4.  It 
is  a  yellowish  liquid,  lighter  than  water,  and  soluble  in 
alcohol  and  ether. 

Sulphate  of  Carbyle  (C4H4,  4$O3)  arises  when  the  va- 
por of  anhydrous  sulphuric  acid  is  absorbed  by  pure  alco- 
hol. It  is  a  white  crystalline  body.  When  dissolved  in 
alcohol,  and  water  added,  the  solution  neutralized  by  car- 
bonate of  baryta,  filtered,  concentrated,  and  then  mixed 
with  alcohol,  the  Ethionate  of  Baryta  precipitates.  This, 
when  decomposed  by  dilute  sulphuric  acid,  yields  Hydra- 
ted  Ethionic  Acid,  the  constitution  of  which  is  C4H5O, 
4*SO3  +  2HO.  Ethionic  acid  yields  a  series  of  salts, 
many  of  which  can  be  obtained  in  crystals.  On  being 
boiled,  solution  of  ethionic  acid  yields  sulphuric  acid  and 
Isethionic,  the  peculiarity  of  which  is,  that  it  is  isomeric 
with  sulphovinic  acid,  both  containing  C^H5O,  2SO3  f- 
HO. 


LECTURE  LXXIII. 

OXYDATION  OF  ALCOHOL. —  The  Acetyle  Group. — Alde- 
hyde.—  Its  Preparation  and  Properties. — Aldehydic 
Acid. — Davy's  Flameless  Lamp.—*Acetal  produced  by 
Platinum  Black.  —  Acetic  Acid,  Production  of. — Na- 
ture of  the  Change  from  Alcohol  to  Acetic  Acid. — Salts 
of  Acetic  Acid. 

IT  has  been  already  stated  (Lecture  LXXL),  that  when 
alcohol  is  burned"  in  contact  with  oxygen  gas  or  atmos- 
pheric air,  the  sole  products  of  the  combustion  are  car- 
bonic acid  gas  and  water.  But  when  the  oxydation  is 

Under  what  circumstances  does  the  heavy  oil  of  wine  form  ?  How  is 
sweet  oil  of  wine  prepared?  What  are  etherine  and  etherole?  When 
tlr*  vapor  of  anhydrous  sulphuric  acid  is  passed  into  pure  alcohol,  what  is 
tf  ?  result  ?  How  are  ethionic  and  isethionic  acids  prepared  ? 


ALDEHYDE.  331 

partial,  the  hydrogen  is  removed  by  preference,  and  a  new 
series  of  bodies  is  the  result,  designated  as 

The  Acetyle  Series. 

Acetyle,  C4H3 '=  Ac. 

Oxide  of  acetyle =  AcO. 

Hydrated  oxide  of  acetyle  (aldehyde)  .  .  =  AcO  -f  HO. 
Acetylous  acid  (aldehydic  acid)  .  .  .  .  =  AcO$  -f-  HO. 
Acetic  acid =  AcOz  -f  HO. 

Acetyle  is  an  ideal  body,  differing  from  ethyle  by  con- 
taining only  three  atoms  of  hydrogen  instead  of  five.  Its 
oxide,  also,  has  not  yet  "been  insulated. 

Hydrated  Oxide  of  Acetyle— AldeJiyde — may  be  ob- 
tained by  distilling  two  paits  of  the  compound  of  aldehyde 
and  ammonia,  dissolved  in  two  parts  of  water,  with  a  mix- 
ture of  three  of  oil  of  vitriol  and  four  of  Water,  and  redis- 
tilling the  product  from  chloride  of  calcium  at  a  low  tem- 
perature. I\  is  a  colorless  liquid,  of  a  suffocating  odor. 
Its  density  is  -790,  its  boiling  point  72°  F.  It  is  soluble 
in  water  and  alcohoL  It  slowly  oxydizes  in  the  air,  and 
more  rapidly  under  the  influence  of  the  black  powder  of 
platinum,  producing  acetic  acid.  Heated  with  caustic 
potash,  it  yields  aldehyde  resin,  a  brown  body  of  a  resin- 
ous aspect.  Aldehyde  has  received  its  name  from  the 
circumstance  that  it  contains  the  elements  of  alcohol  mi- 
nus two  atoms  of  hydrogen  (Alcohol  Dehydrogenatus). 

When  pure  aldehyde  is  kept  for  a  length  of  time  at 
32°  F.  in  a  close  vessel,  it  yields  Elaldehyde,  a  substance 
isomeric  with  itself,  but  possessing  different  properties, 
the  specific  gravity  of  its  vapor,  for-example,  being  three 
times  that  of  the  vapor  of  aldehyde.  pv-  270. 

From  it  there  is  also  produced,  at  com- 
mon temperatures,  a  second  isomeric 
body,  Metaldehyde. 

Aldehydic  Acid  may  be  obtained  by 
digesting  oxide  of  silver  with  alde- 
hyde, and  precipitating  the  metal  with 
sulphureted  hydrogen.  It  contains 
one  atom  of  oxygen  less  than  acetic 
acid,  and  is  one  of  the  products  of  the 
slow  combustion  of  ether  in  Davy's 
flameless  lamp,  which  may  be  made 

What  is  acetyle?  How  is  aldehyde  prepared?  What  are  its  proper- 
ties  ?  From  what  is  its  name  derived  ?  Under  what  circumstances  do 
elaldehyde  and  metaldehyde  form  ?  What  is  Davy's  flameless  lamp  ? 


332  PREPARATION    OF    VINEGAR. 

by  putting  a  small  quantity  of  ether  in  a  jar  (Fig.  270, 
page  331),  and  suspending  in  the  vapor,  as  it  mixes  with 
atmospheric  air,  a  coil  of  platina  wire  which  has  recently 
been  ignited.  The  wire  remains  incandescent  as  long  as 
any  ether  is  present.  The  same  result  is  obtained  by 
putting  a  spiral  of  platina  wire,  or  a  ball  of  spongy  pla- 
tina, over  the  wick  of  a  spirit  lamp,  the  lamp  being  lighted 
for  a  short  time,  and  then  blown  out ;  the  platinum  con- 
tinues incandescent,  evolving  a  peculiarly  acrid  vapor. 

Acetal  (C8H"9O3),  containing  the  elements  of  ether  and 
aldehyde,  is  produced  by  the  oxydation  of  vapor  of  alco- 
hol by  black  powder  of  platinum,  the  alcohol  being  placed 
in  ajar,  with  moistened  platinum  black  in  a  capsule  above 
it.  In  the  course  of  several  days  the  alcohol  will  be 
found  to  have  become  sour  ;  it  is  then  to  be  neutralized 
with  chalk  and  distilled.  Chloride  of  calcium  separates 
an  oily  liquid  from  the  distilled  product.  This,  on  being 
distilled  at  a  temperature  of  200°  F.,  yields  acetal.  It  is 
a  colorless  and  aromatic  liquid,  lighter  than  water,  and 
boiling  at  203°  F.  It  yields,  under  the  influence  of  an 
alcoholic  solution  of  caustic  potash,  by  absorbing  oxygen 
from  the  air,  resin  of  aldehyde. 

Acetic  Acid — jPyroligneous  Acid — Vinegar  \C^H^Oz-\- 
HO). — When  dilute  alcohol  is  dropped  on  platina  black, 
oxydation  takes  place,  and  the  vapors  of  acetic  acid  are 
Fig.  271.  formed.  On  the  large  scale  it  is  also 
formed  by  allowing  a  mixture  of  alcohol, 
water,  and  a  small  quantity  of  yeast,  b, 
JFV^.*271,  to  flow  over  wood  shavings 
which  have  been  steeped  in  vinegar  con- 
tained in  a  barrel  through  which  atmos- 
pheric air  is  allowed  to  circulate  by  the 
apertures  c  c  c.  The  temperature  rises, 
and  the  acetification  goes  on  with  rapid- 
ity, the  product  being  collected  in  the  re- 
ceiver, d.  Vinegar,  also,  is  formed  by  the  spontaneous 
souring  of  wines  or  beer  containing  ferment,  and  kept  in 
a  cask  to  which  atmospheric  air  has  access.  During  the 
destructive  distillation  of  dry  wood,  acetic  acid  (hence 

Mention  some  of  its  products.  What  is  the  constitution  of  acetal? 
How  may  it  be  prepared  by  platinum  black?  Mention  some  of  the  differ- 
ent methods  by  which  acetic  acid  may  be  made.  Why  is  it  sometimes 
called  pyroligneous  acid  ? 


ACETIC    ACID.  333 

called  pyroligneous  acid)  in  an  impure  state  is  found 
among  the  products. 

The  strongest  acetic  acid  may  be  made  by  distilling 
powdered  anhydrous  acetate  of  soda  with  three  times  its 
weight  of  oil  of  vitriol.  The  product  is  then  re-distilled, 
and  exposed  to  a  low  temperature,  when  crystals  of  hy- 
drated  acetic  acid  form;  the  fluid  portion  is  poured  oft', 
and  the  crystals  suffered  to  melt.  It  is  a  colorless  liquid, 
which  crystallizes  below  60°  F. ;  has  a  very  pungent  odor, 
and,  placed  on  the  skin,  blisters  it ;  boils  at  248°  F.,  the 
vapor  being  inflammable.  It  dissolves  in  water,  alcohol, 
and  ether ;  and  in  a  less  pure  state,  as  vinegar,  its  taste, 
odor,  and  applications  are  well  known.  If  its  constitution 
be  compared  with  that  of  alcohol, 

Alcohol    \  '.'  .    :. CiHtOi, 

Acetic  acid C±H±O±, 

it  is  seen  to  differ  from  that  substance  in  the  circumstance 
that  two  hydrogen  atoms  have  been  removed  from  the  al- 
cohol, and  their  places  taken  by  two  oxygen  atoms.  Hence 
the  various  processes  for  its  production  are  easily  ex- 
plained. Acetic  acid  gives  rise  to  several  important  salts. 

Acetate  of  Potash  (KO,  C4jH"3O3)  is  obtained  by  neutraliz- 
ing acetic  acid  with  carbonate  of  potash,  evaporating  to 
dryness,  and  fusing.  This  salt  is  very  deliquescent,  and 
has  an  alkaline  reaction. 

Acetate  of  Soda  is  made  on  the  large  scale  by  saturating 
the  impure  pyroligneous  acid  formed  in  the  destructive 
distillation  of  wood,  with  lime,  and  then  decomposing  the 
acetate  of  lime  with  sulphate  of  soda.  The  sulphate  of 
lime  precipitates,  the  solution  being  crystallized,  ancl  the 
crystals  subsequently  purified  by  draining,  fusing,  solu- 
tion, and  re-crystallization.  The  crystals  effloresce  in  the 
air,  and  are  soluble  in  water  and  alcohol. 

Acetate  of  Ammonia — Spirit  of  Minder  erus. — The  solu- 
tion is  made  by  saturating  acetic  acid  with  carbonate  of 
ammonia,  and  the  solid  by  distilling  acetate  of  lime  and 
bydrochlorate  of  ammonia;  the  acetate  of  ammonia  passes 
over,  and  chloride  of  calcium  is  left. 

Acetate  of  Alumina  is  made  by  the  decomposition  of  a 

What  change  does  alcohol  undergo  in  passing  into  acetic  field  ?  Men- 
tion some  of  the  more  important  salts  of  acetic  acid.  BLOW  is  r}ie  acetate 
of  soda  made  ?  What  is  the  spirit  of  Min  lor.sn.is  ? 


334.  SALTS    OF    ACETIC    ACID. 

solution  of  alum  by  acetate  of  lead.     It  is  much  used  by 
dyers  as  a  mordant. 

Acetates  of  Lead. — 1st.  Neutral  Acetate  (Sugar  of  Lead) 
may  be  made  by  dissolving  litharge  in  acetic  acid.  It 
occurs  in  colorless  prismatic  crystals,  and  also  in  crys- 
talline masses.  It  has  a  sweetish,  astringent  taste,  from 
which  its  commercial  name  is  derived.  It  is  soluble  in 
about  its  own  weight  of  cold  water.  The  crystals  efflo- 
resce in  the  air.  2d.  Subacetates  of  Lead — Scsquibasic 
Acetate — is  formed  by  partially  decomposing  the  neutral 
acetate  by  heat.  Its  solution  is  known  as  Goulard's  Wa- 
ter. Two  other  subacetates  may  be  made  byrthe  action 
of  ammonia  on  the  neutral  salt.  Their  solutions  have  an 
alkaline  reaction,  absorb  carbonic  acid  from  the  air,  and 
give  rise  to  a  precipitate  of  the  basic  carbonate. 

Acetates  of  Copper. — 1st.  Neutral  Acetate  —  Distilled 
Verdigris  —  made  '  by  dissolving  verdigris  in  hot  acetic 
acid.  On  cooling,  it  yields  green  crystals^  soluble  both 
in  water  and  alcohol.  It  is  used  as  a  paint.  2d.  Bibasic 
Acetates  of  Copper- —  Verdigris — may  be  made  by  the  ac- 
tion of  vinegar  and  air  conjointly  on  metallic  copper. 
Verdigris  is  a  mixture  of  several  acetates,  one  of  which 
may  be  obtained  by  digesting  it  in  warm  water;  a  second 
arises  on  boiling  this ;  the  insoluble  residue  of  the  verdigris 
contains  a  third. 


LECTURE  LXXIV. 

DERIVATIVES   OF  AcETYLE.-1— THE  KAKODYLE   GROUP. — 

Chloracetic  Acid. — Acetone. —  Chloral  and  Heavy  Mu- 
riatic Ether. — Substitutions  of  Chlorine  in  Light  Mu- 
riatic Ether. — Sulphur-alcohol. — Its  Relations  to  Mer- 
cury.— Xanthic  Acid.— The  Kakodyle  Group. —  Oxide. 
— Chloride. — Kakodylic  Acid. 

CHLORACETIC  Acid  ( C4H04C13). — Thi6  remarkable  body 
is  formed  when  a  small  quantity  of  crystallized  acetic 
acid  is  exposed  to  the  sunshine  iii  a  jar-full  of  chlorine 
gas.  The  crystals  which  form  on  the  inside  of  the  vessel 

For  what  purpose  is  acetate  of  alumina  used  ?  What  varieties  of  ace- 
tate of  lead  are  there,  and  how  are  they  formed  ?  What  are  the  varieties 
of  acetate  of  copper  ?  How  is  chloracetic  acid  made  ? 


DERIVATIVES    OF   ACETYLE.  335 

are  to  be  dissolved  in  water,  and  the  solution  evaporated 
in  vacuo  with  capsules  containing  caustic  potash  and  oil 
of  vitriol.  A  little  oxalic  acid  is  first  deposited,  and  then 
the  chloracetic  acid  crystallizes  as  a  colorless  and  deli- 
quescent body,  with  a  powerfully  acid  taste,  and  capable 
of  corroding  the  skin.  It  melts  at  115°  F.,  and  boils  at 
390°.  By  comparing  its  constitution  with  that  of  acetic 
acid,  it  will  be  seen  that  in  its  formation  three  atoms  of 
chlorine  have  been  substituted  for  three  of  hydrogen.  It 
yields  an  extensive  series  of  salts; 

Acetone— Pyroacetic  Spirit  (C-H.jO) — may  be- made  by 
passing  acetic  acid  vapor  through  a  red-hot  iron  tube, 
or  by  the  distillation  of  dry  acetate  of  lead.  It  is  a  ..lim- 
pid, colorless,  and  volatile  liquid,  boiling  at  132°,  burns 
with  a  bright  flame,  and  is  soluble  in  water  and  alcohol. 
NordhauSen  oil  of  vitriol,  distilled  with  acetone,  abstracts 
from  it  One  atom  of  water,  yielding  an  oily  body,  the  con- 
stitution of  which  is  C3H.2 ;  it  is  lighter  than  water,  and 
has  an  odor  of  garlic. 

Sir  R.  Kane  considers  acetone  to  be  the  hydrated  ox- 
ide of  an  ideal  radical,  Mesityle,  C^H^  and  has  been  able 
to  produce  the  oxide  and  chloride  of  meskyle.  Zeise  also 
discovered  a  compound  consisting  of  the  oxide'  of  mesityle 
and  bichloride  of  platinum. 

CHLORAL  (C±HCIZO2). — When  dry  chlorine  is  passed 
into  anhydrous  alcohol,  and  the  action  finished  by  the  ai$ 
of  heat,  hydrochloric  acid  is  produced  ;  and  on  its  ceasing 
to  appear,  if  the  product  be  agitated  with  three  times  its 
volume  of  oil  of  vitriol,  and  the  mixture  warmed,  an  oily 
liquid  floats  on  the  acid  :  this  is  chloral.  It  may  be  puri- 
fied by  successive  distillation  from  oil  of  vitriol  and  quick- 
lime. It  is  an  oily,  colorless  liquid,  which  causes  a  flow  of 
tears,  leaves  a  transient  greasy  stain  upon  paper,  has  a 
density  of  1*502,  boils  at  201°,  is  soluble  in  water  and  al- 
cohol ;  it  yields  no  precipitate  with  nitrate  of  silver.  -When 
kept  for  a  length  of  time  in  a  sealed  tube,  it  spontaneous- 
ly becomes  a  white,  solid,  insoluble  chloral.  In  this  con- 
dition it  is  little  soluble  in  water,  and  reverts  to  its  other 
state  by  being  warmed. 

If  chlorine  acts  on  alcohol  containing  water,  heavy  Mu- 

What  is  the  relationship  between  acetic  and  chloracetic  acid  ?  What 
is  the  mode  of  preparing  pyroacetic  spirit  ?  What  is  mesityle  ?  What 
is  chloral  ?  Under  what  circumstances  does  insoluble  chloral  form  ? 


336  SULPHUR-ALCOHOL. 

rlatic  Ether  is  formed.  It  is  a  colorless  and  volatile 
liquid^ 

The  action  of  chlorine  upon  common  ether,  and  also  on 
the  compound  ethers^  is  very  interesting.  It  consists  in 
the  gradual  removal  of  hydrogen,  chlorine  being  substi- 
tuted for  it.  This,  in  many  instances  in  which  the  aid  of 
the  sunlight  is  resorted  to,  terminates  in  the  entire  re- 
moval of  the  hydrogen.  In  the  compound  ethers  it  is  the 
basic  hydrogen  which  is  removed,  while  that  of  the  acid 
escapes,  as  in  the  case  of  chlorureted  acetic  and  chlorureted 
formic  ether-g.  When  the  vapor  of  light  hydrochloric 
ether  is  acted  upon  by  chlorine  gas,  a  complete  series  of 
compounds  may  be  obtained,  the  hydrogen  eventually 
disappearing-: 

Hydrochloric  ether C4ffs  C7>; 

Monochlorureted  hydrochloric  ether  .  .  'C4H^C12 ; 
Bichlorureted  "  .  "  .  .  C^H^Cl* ; 
Trichlorureted  "  •  "  .  .  C4H2Cl^; 
duadrichlorureted  "  "  .  .  C4H  Ch; 
Perchloride  of  carbon C4  Ck'r 

furnishing,  therefore,  a  very  striking  instance  of  the  doc- 
trine of  substitution. 

Mercaptan — Sulphur-alcohol  (C4H6S2) — is  prepared  by 
saturating  a  solution  of  caustic  potash,  specific  gravity 
1*3,  with  sulphureted  hydrogen,  and  distilling  it  with  an 
equal  volume  of  sulphovinate  of  lime  -of  the  same  density. 
It  passes  over  with  water,  on  the  surface  of  which  it 
floats  as  a  colorless  liquid,  specific  gravity  '842,  soluble 
in  alcohol.  It  boils  at  97°,  smells  like  onions,  and  burns 
with  a  blue  flame.  Mercaptan  corresponds  to  alcohol  in 
which  all  the  oxygen  has  been  replaced  by  sulphur;  but 
in  its  action  on  metallic  oxides  it  answers  to  the  hydruret 
of  a  compound  radical,  C4H5S.2.  Thus,  with  peroxide  of 
mercury,  it  forms  a  mercaptide  with  the  production  of 
water;  and  this  may  be  decomposed  by  sulphureted  hy- 
drogen, sulphuret  of  mercury  subsiding,  and  mercaptan 
being  reproduced.  Mercaptan  derives  is  name  from  its 
strong  affinity  for  mercury  (Mercurium  Captans). 

Xantliic  Acid'(C6H5S4O  +  HO}. — Hydrate  of  potash  is 
to  be  dissolved  in  twelve  parts  of  ajcohol,  specific  gravity 
•800,  and  bisulphuret  of  carbon  dropped  into  the  solution 

Describe  the  successive  action  of  chlorine  upon  ether.  What  remark- 
able qualities  does  mercaptan  possess  ?  How  is  it  prepared  ?  From 
what  is  its  name  derived  ?  What  is  the  process  for  preparing  xanthic 
acid? 


KAKODYLE.  337 

until  it  ceases  to  have  an  alkaline  reaction.  On  cooling  to 
zero,  the  xanthate  of  potash  crystallizes :  it  is  to  be  dried 
in  vacuo.  It  is  soluble  in  water  and  alcohol,  but  not  in 
ether ;  and  from  it  xanthic  acid  may  be  procured  by  the 
action  of  dilute  hydrochloric  acid.  Xanthic  acid  is  an 
oily  liquid,  heavier  than  water,  which  first  reddens  and 
then  bleaches  litmus  paper.  At  75°  it  is  decomposed 
into  alcohol  and  bisulphuret  of  carbon.  It  is  also  decom- 
posed by  the  action  of  the  air. 

KAKODYLE  (C4H6As  =  Kd)  is  a  compound  radical, 
which  gives  rise  to  an  extensive  group  of  bodies,  in  which 
it  acts  the  part  of  a  metal. 

The  Kakodyle  Group. 

Kakodyle,  CiHsAs =Kd. 

Oxide  of  kakodyle =  KdO. 

Chloride        "  =  KdC~ 

Iodide  "  =  Kdl. 

Sulphuret      "  =  KdS. 

&c.  &c. 

Kakodyle  may  be  obtained  by  decomposing  the  chlo- 
ride of  kakodyle  with  metallic  zinc  in  an  apparatus  filled 
with  carbonic  acid  gas,  and  may  be  purified  by  re-distil- 
lation from  zinc,  similar  precautions  being  taken  to  -ex- 
clude atmospheric  air.  It  is  a  colorless  liquid,  of  a  pow- 
erful odor,  taking  fire  on  the  contact  of  air,  oxygen  gas, 
or  chlorine;  boils  at  338°,  crystallizes  at  21°,  and  is  de- 
composed by  a  red  heat  into  olefiant  gas,  light  carbureted 
hydrogen,  and  arsenic. 

Oxide  of  Kakodyle — Alkarsine—  Cadet's  Fuming  Liquor 
— is  prepared  by  the  distillation  of  acetate  of  potash  and 
arsenious  acid,  receiving  the  products  in  an  ice-cold  vessel 
the  temperature  being  finally  carried  to  a  red  heat.  The 
oxide  comes  over  in  an  impure  state,  sinking  to  the  bot- 
tom of  the  other  products.  It  is  to  be  decanted,  washed 
with  water,  boiled,  and  then  distilled  in  a  vessel  full  of 
hydrogen  from  hydrate  of  potash.  It  is  a  colorless  li- 
quid, specific  gravity  1*462,  boils  at  300°,  and  solidifies  at 
9°  ;  is  sparingly  soluble  in  water,  but  more  so  in  alcohol ; 
is  excessively  poisonous,  possessing  a  concentrated  smell 
like  garlic.  Heated  in  the  air,  it  burns,  producing  car- 
bonic acid,  water,  and  arsenious  acid. 

Chloride  of  Kakodyle  may  be  procured  by  the  action  of 

What  is  its  action  on  litmus  paper  ?    What  is  kakodyle  ?     How  may  it 
be  isolated  ?     What  are  alkarsine  and  Cadet's  fuming  liquor  ?     How  is  it 
prepared,  and  what  are  its  properties? 
F  F 


388  THE    WOOD-SPIRIT    tiKOUP. 

a  dilute  solution  of  corrosive  sublimate  on  a  dilute  alco 
holic  solution  of  oxide  of  kakodyle ;  a  white  precipitate 
falls,  which,  distilled  with  strong  hydrochloric  acid,  yields 
corrosive  ^ublimate,  water,  and  the  chloride  of  kakodyle 
passes  over.  When  purified  by  chloride  of  calcium,  and 
distilled  in  an  atmosphere  of  carbonic  acid,  it  is  a  color- 
less liquid,  of  a  dreadful  odor,  heavier  than  water,  and  iii- 
Boluble  therein,  but  soluble  in  alcohol.  It  is  very  poison- 
ous. It  boils  at  about  212°,  the  vapor  taking  fire  in  the 
air. 

KaJwdylic  Acid — Alcargcn  (Kd  .  O3) — may  be  made  by 
the  action  of  oxide  of  mercury  upon  oxide  of  kakodyle  un- 
der the  surface  of  water,  at  a  low  temperature.  Kakodylic 
acid  forms  crystals  which  deliquesce  in  the  air,  are  soluble 
in  water  and  alcohol,  but  not  in  ether.  It  is  not  acted  upon 
by  oxydizing  agents,  such  as  nitric  acid,  but  is  reduced  to 
oxide  of  kakodyle  by  several  deoxydizing  bodies.  It  is 
not  poisonous. 

Kakodyle  furnishes  a  complete  series  of  bodies  :  the 
iodide,  sulphuret,  cyanide,  and  a  substance  isomeric  with 
the  oxide,  which  has  the  name  of  parakakodylic  oxide. 


LECTURE  LXXV. 

-SriRiT  GROUP. — Methyle. — Its  Oxide  and  Hy- 
drated  Oxide. — Salts  of  Methyle. — Formic  Acid,  natu- 
ral and  artificial  Production  of. — Derivatives  of  l^Vood 
Spirit. — Substitutions  of  Chlorine  in  Oxide  of  Methyle. — 
Substitutions  in  Chloride  of  Methyle. 

IN  the  destructive  distillation  of  wood  in  the  prepara- 
tion of  pyroligneous  acid,  there  passes  over  a  body  to 
which  the  name  of  wood  spirit  has  been  given.  This  is 
the  hydrated  oxide,  or  alcohol  of  an  ideal  compound  rad- 
ical, passing  under  the  name  of  methyle. 

The  Methyle  Group. 

Methyle,  C2H3 =  Me. 

Oxide  of  methyle     .     .    .    .  =  MeO 
Hydrated  oxide    ......=  MeO  -4-  HO. 

Chloride =  MeGL 

&c.  Sec. 

What  is  the  process  for  preparing  the  chloride  of  kakodyle  1  What  are 
its  properties  1  What  is  the  constitution  of  alcargen  ?  Under  what  cir- 
cumstances is  wood  spirit  produced  ?  What  is  its  ideal  compound  radical  T 


COMPOUNDS    OF    METHYLE.  339 

Oxide  of  Methyle —  Mcthylic  Ether — Wood  Ether 
(C.2H3O). — This  substance  is  made  from  the  hydrated  ox- 
ide on  the  same  principle  that  ether  is  obtained  from  al- 
cohol :  one  part  of  wood  spirit  and  four  of  oil  of  vitriol 
being  heated  in  a  flask,  the  vapor  is  passed  through  a  small 
quantity  of  caustic  potash  solution,  and  received  at  the  mer- 
curial trough.  It  is  a  permanently  elastic  gas,  colorless, 
and  has  a  specific  gravity  of  1*617,  burns  with  a  pale  flame, 
is  very  soluble  in  water,  which  takes  up  thirty-three  times 
its  volume  of  it,  and  yields  it  unchanged  when  heated. 

Hydrated  Oxide  of  Methyle —  Wood  Spirit — Pyroxylic 
Spirit — may  be  separated  from  crude  wood  vinegar  by  dis- 
tillation. It  passes  over  with  the  first  portions  along  with 
a  little  acid,  which,  being  neutralized  with  hydrate  of  lime, 
the  wood  spirit  may  be  separated  from  the  oil  which  floats 
on  its  surface,  and  redistilled.  The  product  thus  obtained 
may  be  rectified  in  the  same  manner  as  common  alcohol, 
and  rendered  anhydrous  by  quicklime.  It  is  then  a  color- 
less liquid,  of  a  hot  taste  and  peculiar  smell.  It  boils  at 
152°,  and  has  a  specific  gravity  of -798  at  68°.  It  is  sol- 
uble in  water,  dissolves  resins  and  oils,  and  may  be  burn- 
ed like  spirit  of  wine.  It  then  exhales  a  peculiar  odor. . 

Chloride  of  Methyle  (MeCl)  may  be  made  from  the  re- 
action of  sulphuric  acid  upon  common  salt  and  wood 
spirit.  It  is  a  colorless  gas,  which  may  be  collected  over 
water;  has  a  density  of  1'731.  It  has  a  peculiar  odor,  is 
inflammable,  and  may  be  decomposed  by  passing  through 
a  red-hot  tube. 

Sulphate  of  Oxide  of  Methyle  (MeO,  SO3)  may  be  pre- 
pared by  distilling  one  part  of  wood  spirit  with  eight  or 
ten  of  oil  of  vitriol ;  the  product  is  to  be  washed  with 
water,  and  redistilled  from  caustic  baryta.  It  is  an  oily, 
neutral  liquid,  smelling  like  garlic  ;  specific  gravity  1-321. 
It  boils  at  370°.  It  is  not  soluble  in  water,  but  is  decom- 
posed by  that  liquid,  especially  at  the  boiling  temperature, 
into  sulphomethylic  acid  and  hydrated  oxide  of  methyle. 
It  is  to  be  observed,  that  in  the  series  of  wine  alcohol 
there  is  no  compound  corresponding  to  this. 

Nitrate  of  Oxide  of  Methyle  (MeO,  NO6)  is  obtained  by 

How  is  the  oxide  of  methyle  prepared,  and  what  is  its  form  ?  What  is 
the  constitution  of  pyroxylic  spirit?  What  are  its  properties,  and  for 
what  purposes  may  it  be  used '?  How  is  the  chloride  of  methyle  prepar- 
ed  ?  In  the  wine  series,  is  there  any  compound  analogous  to  sulphate  of 
oxide  of  methyle  ? 


310  FORMIC    ACID. 

the  action  of  a  mixture  of  wood  spirit  and  oil  of  vitriol 
upon  nitrate  of  potash.  It  is  a  colorless  liquid,  heavier 
than  water ;  boils  at  150°  ;  burns  with  a  yellow  flame. 
Its  vapor  explodes  when  heated.  In  a  solution  of  caustic 
potash,  it  decomposes  into  nitrate  of  potash  and  wood 
spirit. 

Oxalate  of  Oxide  of'MetJiyle  (MeO,  C.2O3)  is  made  by 
distilling  oxalic  acid,  wood  spirit,  and  oil  of  vitriol.  The 
liquid  which  is  collected  is  allowed  to  evaporate ;  it 
yields  crystals  of  the  oxalate.  When  pure,  it  is  colorless  ; 
melts  at  124°,  and  boils  at  322°.  It  is  decomposed  by 
hot  water  into  oxalic  acid  and  wood  spirit,  by  solution  of 
ammonia  into  oxamide  and  wood  spirit. 

Sulphomethylic  Acid  (MeO,  2SO3  +  HO),  the  com- 
pound corresponding  to  sulphovinic  acid,  and  prepared 
in  the  same  way,  by  substituting  wood  spirit  for  alcohol 
It  is  thus  procured  as  a  sirup  or  in  small  crystals,  solu- 
ble in  water  and  alcohol.  It  is  an  instable  body,  and  pos- 
sesses many  analogies  with  sulphovinic  acid. 

Formic  Acid  (C2HO3  +  HO).— This  acid,  in  the  wood- 
spirit  series,  is  the  analogue  of  acetic  acid  in  the  alcohol 
series.  It  maybe  procured  on  principles  similar  to  those 
involved  in  the  preparation  of  acetic  acid,  as  by  the  grad- 
ual oxydation  of  the  vapor  of  wood  spirit  in  the  air  under 
the  influence  of  black  platinum.  In  a  dilute  state  it  may 
be  prepared  by  distilling  one  part  of  sugar,  three  of  per- 
oxide of  manganese,  and  two  of  water,  with  three  parts 
of  sulphuric  acid,  diluted  with  an  equal  weight  of  wa- 
ter. The  liquid  which  distills  is  to  be  neutralized  by 
carbonate  of  soda,  purified  by  animal  charcoal,  and  redis- 
tilled along  with  sulphuric  acid.  It  occurs  naturally  in 
the  bodies  of  red  ants,  and  hence  has  obtained  the  name 
of  formic  acid.  From  the  distillation  of  those  animals  it 
was  originally  procured. 

Anhydrous  formic  acid  (C.2HO3)  obviously  contains 
the  elements  of  two  atoms  of  carbonic  oxide  and  one  of 
water.  It  yields  two  hydrates,  respectively  containing 
one  and  two  atoms  of  water.  The  first,  for  which  the 
formula  has  already  been  given,  is  procured  by  the  ac- 

How  is  the  nitrate  obtained,  and  what  are  its  properties  ?  Describe  the 
preparation  of  the  oxalate  and  of  sulpho-methylic  acid.  What  is  the  con- 
stitution of  formic  acid  ?  How  is  it  procured  1  From  what  circumstance 
is  its  name  derived?  What  are  its  properties? 


DERIVATIVES    OF    METIIYLE.  341 

tion  of  sulphureted  hydrogen  on  formiate  of  lead.  It  is  a 
colorless  liquid,  of  a  strong  odor;  boils  at  212°,  and  crys- 
tallizes below  32°.  It  is  inflammable,  and  has  a  specific 
gravity  of  1-235.  It  blisters  the  skin.  Formic  acid  yields 
a  complete  series  of  salts. 

Chloroform  (C.2HC13)  is  made  by  distilling  wood  spirit 
w>h  a  solution  of  chloride  of  lime.  It  is  a  colorless  liquid  ; 
specific  gravity  1*48  ;  boils  at  141°.  It  burns  with  a 
green  flame,  and  is  decomposed  by  an  alcoholic  solution 
of  potash  into  chloride  of  potassium  and  formiate  of  pot- 
ash. The  relationship  between  formic  acid  and  chloro- 
form is  obvious  :  it  consists  in  the  substitution  of  three 
atoms  of  chlorine  for  three  of  oxygen.  There  are  also 
two  analogous  compounds  : 

Bromoform C2HBr3. 

lodoform C2///3. 

FormometTiylal  (C3H4O.2)  is  prepared  by  distilling  wood 
spirit,  oxide  of  manganese,  and  dilute  sulphuric  acid.  On 
saturating  the  product  with  potash,  formomethylal  sepa- 
rates as  a  colorless  oily  liquid  :  specific  gravity  '855  ; 
boils  at  107°,  and  soluble  in  water. 

Methyle-mercaptan. — Formed  as  the  common  mercap- 
tan,  by  substituting  sulphomethylate  of  potash  for  sulpho- 
vinate  of  lime.  It  is  analogous  to  common  mercaptan. 

When  chlorine  is  made  to  act  on  the  oxide  of  methyle 
at  common  temperatures,  it  removes  one  of  the  hydrogen 
atoms  ;  and  by  continuing  the  action,  a  second  may  be 
taken  away,  and  the  process  of  substitution,  as  shown  in 
the  following  series,  may  be  carried  so  far  as  to  end  in  the 
removal  of  oxygen  and  the  production  of  chloride  of 
carbon. 

Oxide  of  methyle C2H3O.     - 

1st  substitution CZH2O,  Cl. 

2d  " CZH  O,  C72. 

3d  "  C2      O,  C13. 

4th  (chloride  of  carbon)  .  C2  C74. 

Other  methylic  compounds  furnish  similar  series,  thus  : 

Chloride  of  methyle ^   .  C2H3CL 

1st  substitution CZHZC12. 

3d  "  (chloroform)    . .  .     .     .     .  C^H  C13. 

3d  "  (chloride  of  carbon)     .     .  C2       CZ4. 

How  is  chloroform  obtained  ?  "What  is  the  process  for  preparing  for- 
momethylal  ?  Describe  the  series  of  substitutions  of  chlorine  on  the  oxide 
of  methyle.  Describe  the  analogous  substitutions  with  chloride  of  methyle  ? 

FF  2 


342  FUSEL   OIL. 


LECTURE  LXXVI. 

THE  POTATO  OIL   GROUP.  —  Fusel   Oil.  —  Chloride  of 

Amyle.  —  Sulphamylic   Acid.  —  Amilen.  —  Relations  of 

Valerianic  Acid. 
THE  BENZYLE  GROUP.  —  Oil  of  Bitter  Almonds.  —  Benzoic 

Acid.  —  Sulphobenzoic  Acid.  —  Chloride   of  Benzyle.  — 

Benzamide. 

IN  the  distillation  of  brandy  from  potatoes,  a  volatile 
oil  passes  over.  It  is  regarded  as  the  hydrated  oxide  of 
an  ideal  compound  radical,  which  passes  under  the  name 
of  Amyle,  having  the  constitution  C10Hn. 

The  Potato  Oil  Group. 
Amyle,  CioHn    .........  =  Ayl. 

Amyle  ether   ..........  =  AylO. 

Amyle  alcohol  (potato  oil)     .....  =  AylO  -f-  HO. 

Chloride  of  amyle    ........  =  AylCl. 

&.C.  &.C. 

Amilen   .........  CioHio. 

Valerianic  acid 


Of  these,  amyle  and  its  oxide,  amyle-ether,  are  ideal. 

Hydrated  Oxide  of  Amyle  —  Amyle  Alcohol  —  Potato  Oil 
—  Fusel  Oil  (  CWHU  O-}-HO).  —  This  substance  passes  over 
toward  the  end  of  the  first  distillation  of  potato  spirit,  and 
communicates  to  it  a  milky  aspect.  On  standing,  it  floats 
on  the  surface,  and  may  be  purified  by  washing  with  wa- 
ter, drying  with  chloride  of  calcium,  and  redistillation. 
It  is  a  fluid  oil  of  a  suffocating  odor,  which  acts  power- 
fully on  the  animal  system.  Its  specific  gravity  is  '818  ; 
it  boils  at  269°. 

Chloride  of  Amyle  (AylCl}  is  made  by  distilling  equal 
weights  of  potato  oil  and  perchloride  of  phosphorus,  wash- 
ing with  potash  water,  and  redistilling  from  chloride 
of  calcium.  It  is  an  aromatic  liquid,  boils  at  215°,  and 
burns  with  a  green  flame.  Under  the  influence  of  sun- 
shine, eight  of  its  hydrogen  atoms  may  be  removed,  eight 
chlorine  atoms  being  substituted  for  them,  ClQHnCl  yield- 
ing CwH3Clgt  forming  chlorureted  chloride  of  amyle. 

What  is  the  imaginary  radical  of  the  potato  oil  group  ?  What  are  the 
nature  and  relations  of  fusel  oil  ?  What  are  the  properties  of  the  chloride 
of  amyle  ? 


VALERIANIC    ACID.  843 

The  Iodide  and  Bromide  of  Amyle  are  compounds  anal- 
ogous to  the  chloride. 

Acetate  of  Oxide  of  Amyle  is  obtained  by  distilling  ace- 
tate of  potash,  potato  oil,  and  sulphuric  acid. .  It  is  a  col- 
orless liquid,  which  boils  at  257°. 

Sulphamilic  Acid  (AylO,  2SO3H  +  O)  is  generated 
when  sulphuric  acid  is  made  to  act  on  an  equal  weight  of 
potato  oil.  From  this,  by  the  successive  action  of  car- 
bonate of  baryta  and  sulphuric  acid,  it  may  be  procured 
by  operating  on  the  same  principles  as  for  sulphovinic 
acid,  to  which,  both  in  constitution  and  properties,  it  is 
the  analogue.  It  is  a  sirupy  or  crystalline  body,  and  is 
decomposed  by  ebullition  into  potato  oil  and  sulphuric 
acid. 

Amilen  ( C10Hi0)  is  obtained  by  the  action  of  anhydrous 
phosphoric  acid  on  potato  oil ;  it  is  an  oily  liquid  which 
boils  at  320°.  In  constitution  and  position  it,  therefore, 
occupies,  in  the  amyle  series,  the  same  situation  that  ole- 
fiant  gas  does  for  the  wine  alcohol  series,  and,  indeed,  is 
isomeric  with  that  body. 

Valerianic  Acid  ( C10H9O3)  bears  the  same  relation  to  the 
amyle  group  which  acetic  acid  does  to  the  wine  alcohol 
group,  or  formic  acid  to  the  wood  spirit  group.  It  is 
formed  when  warm  potato  oil  is  dropped  on  platinum 
black  in  contact  with  the  air.  It  occurs  naturally  in  the 
root  of  the  Valeriana  Officinalis,  but  is  best  made  by  heat- 
ing potato  oil  in  a  flask,  with  a  mixture  of  quicklime  and 
hydrate  of  potash,  for  several  hours  at  a  temperature  of 
400°.  The  white  residue  is  immersed  in  cold  water,  and 
distilled  with  a  slight  excess  of  sulphuric  acid,  so  as  to 
drive  off  hydrated  valerianic  acid  and  water.  It  is  a  col- 
orless oil  of  an  acid  taste,  combustible,  and  boiling  at  347°. 
When  acted  upon  by  chlorine  in  the  dark,  and  the  action 
aided  by  heat,  it  gives  rise  to  Chlorovalerisic  Acid  ( CWH6 
Cl^O3  4-  HO),  in  which  there  has  been  a  removal  of  three 
hydrogen  atoms  and  a  substitution  of  three  of  chlorine. 
Under  the  influence  of  the  sunshine,  by  the  same  process, 
another  hydrogen  atom  is  removed,  and  Chlorovalerosic 
Acid  forms,  its  constitution  being  Ci0H5CltO3  +  HO. 

To  what  substance  is  sulphamilic  acid  analogous  ?  What  relation  is 
there  between  amilen  and  olefiant  gas  7  What  is  the  relation  between 
acetic  and  valerianic  acids  ?  From  what  natural  source  may  the  latter  be 
derived  ?  How  is  it  made  artificially  ?  What  id  the  successive  action  of 
chlorine  upon  it  ? 


344  THIS  BENZYLE  GROUP. 

The  Benzyle  Group. 

Benzyle,  CuHnOz =  Bz. 

Hydruret  of  benzyle =  Bz  -4-  II. 

Oxide  of  benzyle  (benzole  acid)    .    .     .    .  =  Bz  4-  O. 

Chloride =Bz  +  CL 

Sec.  &c. 

Of  this  series,  benzyle,  the  radical,  is  an  ideal  body.  It 
is  a  radical  which  discharges  the  functions  of  a  metallic 
body,  giving  rise  to  oxides,  chlorides,  iodides,  &c.,  as  the 
table  shows. 

Hydruret  of  Benzyle — Oil  of  Bitter  Almonds  (BzH) — is 
obtained  by  the  distillation  of  bitter  almonds,  from  which 
the  fixed  oil  has  been  expressed,  with  water,  and  arises 
from  the  action  of  the  water  upon  Amygdaline  contained 
in  the  seed.  It  may  be  purified  by  distillation  from  pro- 
tochloride  of  iron  with  hydrate  of  lime  in  excess,  and  is  a 
colorless  liquid  of  an  agreeable  odor,  slightly  heavier  than 
water,  and  also  slightly  soluble  therein,  but  very  soluble 
in  alcohol  and  ether.  It  boils  at  356°.  In  the  air  it  pass- 
es into  benzoic  acid  by  absorbing  oxygen. 

Oxide  of  Benzyle — Benzoic  Acid  (BzO  -f  HO).— This 
acid  is  obtained  by  sublimation  from  gum  benzoin,  that 
substance  being  placed  in  a  shallow  vessel,  over  the  top 
of  which  a  cover  of  filtering  paper  is  pasted,  and  this  cov- 
ered by  a  taller  cylinder  of  stouter  paper.  On  heating, 
the  vapors  pass  through  the  filtering  paper,  and,  condens- 
ing in  feathery  crystals  in  the  space  above,  fall  down  upon 
the  paper  and  are  retained  by  it.  A  better  method  is  to 
boil  a  mixture  of  the  gum  with  hydrate  of  lime,  filter, 
concentrate  the  solution,  add  hydrochloric  acid,  and  the 
benzoic  acid  crystalHzes  in  thin  plates  on  cooling.  It  may 
be  subsequently  sublimed.  When  pure  it  has  no  odor. 
It  melts  at  212°,  and  boils  at  462°.  Its  vapor  excites 
coughing.  It  is  much  more  soluble  in  hot  than  in  cold 
water.  It  forms  a  series  of  salts,  and  is  sometimes  used 
for  the  separation  of  iron  from  other  metals. 

Sulphobenzoic  Acid  (C^H5O3,  SO3  +  2HO),  a  bibasic 
acid,  formed  by  the  action  of  anhydrous  sulphuric  acid 
upon  benzoic  acid,  the  mass  being  dissolved  in  water  and 
neutralized  by  carbonate  of  baryta.  On  filtering,  and  add- 

What  is  the  radical  of  the  benzyle  series  ?  What  is  oil  of  bitter  al 
monds  '?  From  what  substance  does  it  arise  ?  What  is  benzoic  acid  ? 
By  what  processes  may  it  be  prepared  ?  What  is  the  process  for  pre 
paring  sulphobenzoic  acid  ? 


DERIVATIVES    OF    BENZYLE.  345 

ing  hydrochloric  acid  to  the  hot  solution,  on  cooling  the 
sulphobenzoate  of  baryta  crystallizes,  which  may  be  de- 
composed by  dilute  sulphuric  acid.  It  is  a  white  crystal- 
line mass. 

Chloride  of  Benzyle  (BzCl). —  When  chlorine  gas  is 
passed  through  oil  of  bitter  almonds,  hydrochloric  acid  is 
formed,  and,  after  expelling  the  excess  of  chlorine  by  heat, 
chloride  of  benzyle  remains. .  It  is  a  colorless  liquid,  of 
a  disagreeable  odor,  heavier  than  water,  combustible,  and 
decomposed  by  boiling  water  into  benzoic  and  hydrochlo- 
ric acids. 

Benzamide  ( Ci4Hr NO3)  is  formed  by  the  action  of  chlo- 
ride of  benzyle  on  dry  ammonia,  the  hydrochlorate  of  am- 
monia being  removed  from  the  resulting  white  mass  by 
cold  water.  From  a  solution  in  boiling  water,  the  ben- 
zamide  crystallizes.  It  melts  at  239°.  It  corresponds 
in  its  chemical  relations  to  oxamide. 

Hydrobenz amide  (C42HiSN2),  made  by  the  action  of  pure 
oil  of  bitter  almonds  on  solution  of  ammonia,  the  product 
being  washed  with  ether,  and  from  its  alcoholic  solution 
this  substance  crystallizes ;  but  when  impure  almond  oil 
is  employed,  three  other  compounds  may  be  obtained : 
they  are  benzhydramide,  azobenzoyle,  and  nitrobenzoyle. 


LECTURE  LXXVII. 

THE  SALICYLE  AND  CINNAMYLE  GROUPS. — Benzoine,  Ben- 
zone,  Benzine. — Hippuric  Acid. — THE  SALICYLE  GROUP. 
— Artificial  Formation  of  Oil  of  Spircea. — Compounds 
of  Salicyle. — Melanic  Acid. — THE  CINNAMYLE  GROUP. 
—  Compounds  of  Cinnamyle. 

BENZOINE  (C14JJ6O.2),  a  body  isomeric  with  bitter  al- 
mond oil.  It  is  found  in  the  residue  after  purify ing~  that 
oil  from  hydrocyanic  acid  by  distillation  from  lime  and 
oxide  of  iron,  and  may  be  obtained  by  dissolving  out  those 
bodies  by  hydrochloric  acid.  It  crystallizes  from  an  alco- 
holic solution,  on  cooling,  in  colorless  crystals,  which  melt 
at  248°.  It  dissolves  in  an  alcoholic  solution  of  caustic 

How  is  the  chloride  of  benzyle  made  ?  How  are  benzamide  and  hydro- 
benz  amide  formed  ?  What  relation  does  benzoine  bear  to  oil  of  bitter 
almonds  ? 


346  DERIVATIVES    OF    BENZYLE. 

potash,  which,  by  boiling  until  the  violet  color  has  disap- 
peared, furnishes  benzilate  of  potash,  a  salt  from  which 
benzilic  acid  may  be  obtained  by  hydrochloric  acid.  The 
constitution  of  Benzilic  Acid  is  C^H^O*,  -f  HO. 

Benzone  (CnHbO)  is  obtained  by  the  distillation  of  dry 
benzoate  of  lime  at  a  high  temperature,  carbonate  of  lime 
remaining  behind.  The  decomposition  is  interesting,  the 
ben  zoic  acid  atom  being  divided,  and  yielding  benzone 
and  carbonic  acid. 

C14H,03  ...  =  ...  CuHbO  +  CO,. 

Benzine  (CuH&)  arises  when  crystallized  benzoic  acid 
is  distilled  from  hydrate  of  lime  at  a  red  heat.  It  is  an 
oily  liquid,  and,  after  being  separated  from  the  water  which 
comes  over  with  it,  is  to  be  rectified.  It  boils  at  187°,  so- 
lidifies at  32°,  and  is  lighter  than  water.  In  its  formation 
the  hydrated  benzoic  acid  is  resolved  into  benzine  and 
carbonic  acid. 


Sulphobenzide  (CnH-0SO^)  is  formed  by  taking  the  sub- 
stance which  arises  from  the  union  of  benzine  with  anhy- 
drous sulphuric  acid,  and  acting  upon  it  with  an  excess 
of  water.  The  sulphobenzide,  which  is  insoluble  in 
that  liquid,  may  be  obtained  in  crystals  from  its  ethereal 
solution.  It  melts  at  212°  F.  From  the  acid  liquid  from 
which  it  has  been  separated  hyposulphobenzic  acid  may 
be  obtained.  Its  constitution  is  C^HbSzOb-{-HO. 

Nitrobenzide  (C^HbNO4),  produced  by  the  action  of 
fuming  nitric  acid  on  benzine,  with  the  aid  of  heat.  It  is 
an  oily  liquid,  of  a  sweet  taste,  heavier  than  water,  and 
boiling  at  415°.  From  it  Azobenzide  (C^H^N)  may  be 
obtained  by  distillation  with  an  alcoholic  solution  of  caus- 
tic potash,  in  the  form  of  red  crystals. 

Chlorbenzine  (  C1ZH&C16)  is  formed  by  the  union  of  ben- 
zine and  chlorine  in  the  sun-rays.  When  distilled,  the 
solid  yields  hydrochloric  acid  and  a  liquid,  Chlorbenzide 


Hippuric  Acid  (C18HSNO5+  HO]  is  found  in  the  urine 

What  is  the  result  of  the  distillation  of  dry  benzoate  of  lime  ?  What 
is  the  nature  of  the  decomposition  ?  What  is  the  result  of  the  distillation 
of  crystallized  benzoic  acid  and  hydrate  of  lime  ?  What  is  the  result  of 
the  action  of  anhydrous  sulphuric  acid  and  benzine  ?  What  is  the  action 
of  nitric  acid  on  benzine  ?  What  substance  results  from  the  union  of  ben- 
zine and  chlorine  ?  From  what  sources  may  hippuric  acid  be  obtained  1 


THE    8ALICYLE     GROUP.  347 

ot  graminivorous  animals,  and  occurs  in  the  urine  of  per- 
sons who  have  taken  benzoic  acid.  It  may  be  prepared 
by  evaporating  the  fresh  urine  of  the  cow,  and  acidulating 
the  concentrated  liquor  with  hydrochloric  acid ;  crystals 
of  hippuric  acid  are  deposited,  which  may  be  decolorized 
by  bleaching  liquor  and  hydrochloric  acid.  It  crystallizes 
in  square  prisms,  sparingly  soluble  in  cold  water,  of  a  bit- 
ter taste  and  acid  reaction.  By  a  high  temperature  or  the 
action  of  sulphuric  acid,  it  yields  benzoic  acid. 

THE  SALICYLE  GROUP. 

There  is  contained  in  the  bark  of  the  willow  and  other 
trees  a  bitter  crystalline  principle,  SALICINE  (C2lHl3On). 
This  substance  may  be  extracted  by  boiling  the  bitter  bark  . 
in  water,  and  digesting  the  concentrated  solution  with  ox- 
ide of  lead  to  decolorize  it,  removing  any  dissolved  lead 
by  sulphureted  hydrogen,  and  evaporating  until  the  sali- 
cine  crystallizes.  It  forms  white  needles  of  a  bitter  taste, 
much  more  soluble  in  hot  than  cold  water.  Distilled  with 
bichromate  of  potash  and  sulphuric  acid,  it  yields  hydro- 
salicylic  acid,  or  the  artificial  oil  of  meadow  sweet,  a  sub- 
stance containing  Salicyle,  the  ideal  compound  radical  of  a 
series  of  bodies. 

The  Salicyle  Group. 

Salicyje,  CnH.,0^ =  SI. 

Hydrosalicylic  acid =  SlH. 

Iodide  of  salicyle =811. 

Chloride =  SICl. 

&c.  &c. 

Hydrosalicylic  Acid — Oil  of  Spircea  Ulmarta,or  Mead- 
ow Sweet  (C^H^O^H] — is  prepared  by  distilling  one 
part  of  salicine,  one  of  bichromate  of  potash,  two  and  a 
half  of  sulphuric  acid,  and  twenty  of  water;  the  salicine 
being  dissolved  in  one  portion  of  the  water,  and  the  acid 
mixed  with  the  rest.  The  yellow  oil  which  comes  over 
is  rectified  from  chloride  of  calcium.  It  may  also  be  ob- 
tained by  distilling  the  flowers  of  meadow  sweet  with 
water.  It  is  transparent,  but  turns  red  in  the  air.  It  is 
slightly  soluble  in  water,  and  very  soluble  in  alcohol.  Its 
specific  gravity  is  T173  ;  it  boils  at  385°  F.  It  contains 
the  same  elements  as  benzoic  acid. 

Salicylic  Acid  (CnH4O4-\-O)  is  obtained  by  the  action 

Under  what  circumstances  does  benzoic  acid  produce  it  ?  From  what 
is  salicine  obtained  ?  "What  is  the  constitution  of  salicyle  ?  How  may 
the  oil  of  meadow  sweet  be  made  artificially  ? 


348  COMPOUNDS    OF    SALICYLE. 

of  hydrate  of  potash  on  the  foregoing  body  by  the  assist- 
ance of  heat.  After  the  disengagement  of  hydrogen  is 
over,  the  mass  is  dissolved  in  water,  and  salicylic  acid 
separates  in  crystals  on  the  addition  of  hydrochloric  acid. 
It  is  more  soluble  in  hot  than  cold  water,  and  is  charred 
by  hot  oil  of  vitriol. 

Chloride  of  Salicyle  (Cl4H5O4Cl)is  made  by  the  action 
of  chlorine  on  hydrosalicylic  acid.  Its  crystals  are  insol 
uble  in  water,  but  soluble  in  solutions  of  fixed  alkalies, 
from  which  it  separates  on  the  addition  of  an  acid,  resist- 
ing decomposition  even  when  boiled  in  caustic  potash. 
It  unites  with  caustic  potash. 

Bromide  and  Iodide  of  Salicyle  also  exist,  but  are  not 
of  interest. 

Chlorosamide  (C^H15N6OdCl3). — Ammoniacal  gas  is  ab- 
sorbed by  the  chloride  of  salicyle,  producing  a  yellow 
body,  which  crystallizes  from  a  boiling  ethereal  solution. 
It  is  insoluble  in  water.  When  acted  upon  by  hot  acids,  it 
yields  a  salt  of  ammonia  and  chloride  of  salicyle ;  an  al- 
kali forms  with  it  ammonia  and  chloride  of  salicyle.  There 
is  an  analogous  bromosamide. 

Salicyluret  of  Potassium  (KSl)  is  formed  by  the  action 
of  oil  of  meadow  sweet  on  a  solution  of  caustic  potash.  It 
forms  in  yellow  crystals  from  its  alcoholic  solution,  and 
has  an  alkaline  reaction. 

Melanic  Acid  (C10H±O5)  is  produced  when  the  crystals 
of  salicyluret  of  potassium  are  exposed  in  a  moist  state  to 
the  air.  They  first  turn  green  and  then  black,  and  alcohol 
extracts  from  them  melanic  acid. 

CINNAMYLE. 

The  essential  oil  of  cinnamon  is  supposed  to  be  the  hy- 
druret  of  an  ideal  compound  radical,  cinnamyle,  analo- 
gous to  benzoyle,  and  yielding  a  series. 

The  Cinnamyle  Group. 

Cinnamyle,  CizHiOz =  Ci. 

Hydruret  of  cinnamyle  (oil  of  cinnamon)  .    .    .     .  =  CiH. 
Oxide  (cinriamic  acid)    .    .    .    .  =  CiO. 

Chloride  "  =  CiCl. 

&c.  &c. 

Hydruret  of  Cinnamyle — Oil  of  Cinnamon  ((718.H"703  -f 

•  What  ia  the  constitution  of  salicylic  acid  ?  What  is  the  action  of  am- 
monia on  chloride  of  salicyle  ?  Under  what  circumstances  is  melanic  acid 
produced  ?  What  is  the  essential  oil  of  cinnamon  ?  What  is  the  consti 
tutiou  of  cinnamyle  ? 


AMMONIA.  349 

H] — is  obtained  by  infusing  cinnamon  in  a  solution  of 
salt,  and  then  distilling  the  whole.  It  is  heavier  than 
water,  and  may  be  separated  from  that  liquid  by  contact 
with  chloride  of  calcium. 

Cinnamic  Acid  (Cl&H7O2  +  O)  is  formed  when  oil  of 
cinnamon  is  exposed  to  oxygen  gas,  the  oil  becoming  a 
white  crystalline  mass,  hydrated  cinnamic  acid.  It  may 
also  be  obtained  by  boiling  hard  Tolu  balsam  with  hydrate 
of  lime.  The  cinnamate  of  lime  crystallizes  as  the  solu- 
tion cools,  benzoate  of  lime  remaining  in  solution.  The 
crystals  are  decolorized  by  animal  charcoal,  and  then  de- 
composed by  hydrochloric  acid  ;  from  the  hot  solution 
cinnamic  ackl  crystallizes.  It  melts  at  248°,  and  boils  at 
560°.  It  is  soluble  in  boiling  water  and  in  alcohol;  is 
decomposed  by  hot  nitric  acid,  and  yields  benzoic  acid, 
with  oil  of  vitriol  and  bichromate  of  potash. 

Chlorocinnose  (C18jEr4C7402)  arises  from  oil  of  cinna- 
mon by  the  substitution  of  four  atoms  of  chlorine  for  four 
of  hydrogen,  and  is  made  by  the  action  of  chlorine  on  oil 
of  cinnamon  by  the  aid  of  heat.  It  crystallizes  from  its 
alcoholic  solution  in  colorless  needles. 


LECTURE  LXXVIII. 

THE  NITROGENIZED  PRINCIPLES.  —  AMMONIA  and  its 
Salts.  —  CYANOGEN. — Preparation  and  Properties  of 
Prussia  Acid. — Amygdaline  and  Synaptase. —  The  Cy- 
anides.—  Oxygen  Acids  of  Cyanogen. 

AMMONIA. — I  have  already  described,  in  Lecture  LY, 
the  compounds  of  hydrogen  and  nitrogen,  under  the 
names  of  amidogen,  ammonia,  and  ammonium,  and  have 
also  shown  the  relation  there  is  between  the  salts  of 
potash  and  soda  and  those  of  the  oxide  of  ammonium. 
This  compound  metal  is  a  hypothetical  body;  its  exist- 
ence may,  however,  be  illustrated  by  passing  a  Voltaic 
current  through  a  globule  of  mercury  in  contact  with 
moist  chloride  of  ammonium,  or  by  putting  an  amalgam 
of  mercury  and  potassium  in  a  strong  solution  of  that  salt. 

How  may  cinnamic  acid  be  prepared?  What  is  the  constitution  of 
ohlprocinnose,  and  how  is  it  prepared  ?  What  is  ammonium  ? 

G  Q 


350  COMPOUNDS    OF    AMMONIA. 

The  mercury  rapidly  increases  in  volume,  retaining  its 
metallic  aspect,  becomes  of  the  consistency  of  butter,  with 
a  very  trivial  increase  of  weight ;  the  resulting  substance 
is  the  Ammoniacal  Amalgam.  All  attempts  to  insulate 
ammonium  from  it  have  failed. 

The  most  important  salts  of  ammonia  are  the  following  : 

Chloride  of  Ammonium- Sal  Ammoniac — Muriate  of  Am- 
monia— was  formerly  brought  from  Egypt,  but  is  now 
made  from  the  ammoniacal  liquors  resulting  from  the 
destructive  distillation  of  animal  matters,  coal,  &c.  It  is 
soluble  in  water,  crystallizes  in  cubes  or  octahedrons,  and 
sublimes  below  a  red  heat  unchanged.  It  is  decomposed 
by  lime  and  potash,  and  is  formed  when  the  vapors 
of  ammonia  mingle  with  those  of  muriatic  acid. 

Nitrate  of  Ammonia  is  formed  by  neutralizing  nitric 
acid  with  ammonia.  It  is  deliquescent,  and  therefore 
very  soluble  in  water.  It  melts  at  240°,  and  at  a  higher 
temperature  decomposes  into  steam  and  protoxide  of  ni- 
trogen, as  is  explained  in  Lecture  XLV. 

Carbonates  of  Ammonia. — The  neutral  carbonate  only 
exists  in  combination.  With  the  carbonate  of  water  it 
unites,  forming  Bicarbonate  of  Ammonia,  which  may  be 
prepared  by  washing  the  commercial  Sesquicarbonate  with 
water  or  alcohol,  which  leaves  it  undissolved.  The  car- 
bonate of  ammonia  of  commerce  is  prepared  by  sublima- 
tion from  a  mixture  of  sal  ammoniac  and  chalk.  Its  con- 
stitution is  not  uniform,  though  it  is  commonly  regarded 
as  a  sesquicarbonate. 

Sulphate  of  Ammonia  may  be  made  by  neutralizing 
sulphuric  acid  with  carbonate  of  ammonia.  It  is  soluble 
in  twice  its  weight  of  cold  water,  and  crystallizes  in  six- 
sided  prisms. 

Hydrosulphuret  of  Ammonia  is  made  by  passing  sul- 
phureted  hydrogen  into  water  of  ammonia  until  no  more 
is  absorbed.  Though  colorless  at  first,  it  absorbs  oxygen, 
and,  sulphur  being  liberated,  it  turns  yellow.  It  is  of 
considerable  use  as  a  metallic  test. 

CYANOGEN. — Bicarburct  of  Nitrogen  (C2N). — The  mode 
of  preparing  this  remarkable  body,  and  also  its  leading 

How  is  the  ammoniacal  amalgam  prepared  ?  From  what  sources  is  sal 
ammoniac  derived  ?  For  what  purpose  is  nitrate  of  ammonia  employed  ? 
What  is  the  carbonate  of  ammonia  of  commerce  ?  How  is  hydrosulphuret 
of  ammonia  made,  and  what  is  its  use  ?  What  is  the  constitution  of  cy- 
anogen ? 


HYDROCYANIC    ACID.  351 

properties,  have  been  described  in  Lecture  LV.  It  is  ot 
great  interest  in  organic  chemistry,  as  being  the  first  dis- 
tinctly established  compound  radical,  and  the  best  repre- 
sentative of  the  electro-negative  class  of  those  bodies. 

We  may  call  to  mind  that  it  is  easily  made  by  the  de- 
composition of  cyanide  of  mercury  at  a  low  red  heat,  is 
a  gaseous  body,  soluble  in  water,  and,  therefore,  must  be 
collected  over  mercury.  It  is  combustible,  and  burna 
v**1*  -  ^urple  flame. 

Tlie  Cyanogen  Group. 


Cyanogen,  C2N =  Cy. 

Hydrocyanic  acid =  CyH. 

Cyanic  acid =  CO. 


Pulminic  acid ^=.Cy^Oz- 

Cyanuric  acid =  Cty3O3. 

&c.  &c. 

Paracyanogen  ( C.2N). — When  the  cyanide  of  mercury  is 
decomposed  in  the  process  for  preparing  cyanogen,  a 
brownish  substance  is  set  free,  which  is  paracyanogen.  It 
is  insoluble  in  water  and  alcohol,  and  is  only  remarkable 
in  being  isomeric  with  cyanogen. 

Hydrocyanic  Acid — Prussic  Acid — Cyanide  of  Hydro- 
gen (C2iV-f-  jff). — Hydrocyanic  acid  may  be  obtained  in  a 
state  of  purity  by  passing  dry  sulphureted  hydrogen  gas 
over  dry  cyanide  of  mercury  in  a  tube,  and  conducting 
the  vapor,  which  is  evolved  when  the  tube  is  warmed,  into 
a  vial  immersed  in  a  freezing  mixture.  The  result  of  the 
decomposition  is  sulphuret  of  mercury  and  hydrocyanic 
acid.  In  a  state  of  aqueous  solution,  it  is  best  obtained  by 
the  action  of  dilute  sulphuric  acid  on  the  ferrocyanide  of 
potassium  in  a  retort,  and  receiving  the  vapor  in  a  Liebig's 
condenser.  Having  ascertained  the  strength  of  the  prod- 
uct, it  may  then  be  diluted  to  the  proper  point.  This  ex- 
amination may  be  conducted  by  precipitating  a  known 
weight  of  the  acid  with  nitrate  of  silver  in  excess,  collect- 
ing the  cyanide  of  silver  on  a  weighed  filter,  washing, 
drying,  and  reweighing,  which  gives  the  weight  of  the 
cyanide.  This,  divided  by  five,  is  the  weight  of  the  pure 
hydrocyanic  acid,  nearly. 

Anhydrous  hydrocyanic  acid  is  a  colorless  and  very  vol- 
atile liquid,  which  exhales  a  strong  odor  of  peach  blooms ; 

What  interesting  fact  is  connected  with  its  discovery  ?  What  are  it* 
properties  ?  What  is  paracyanogen  ?  How  may  hydrocyanic  acid  be 
made  ?  By  what  process  can  its  strength  be  determined  ? 


352  AMYGDALINE. 

has  a  density  of -705  ;  boils  at  79°.  It  mixes  with  water 
and  alcohol  in  any  proportion.  A  drop  of  it  held  in  the 
air  on  a  glass  rod  becomes  solidified  by  the  rapid  evapora- 
tion from  its  surface.  In  the  sunlight  it  decomposes  rap- 
idly, producing  a  dark-colored  substance  ;  and  the  same 
change  goes  on,  though  much  more  slowly,  in  the  dark. 
It  is  one  of  the  most  insidious  and  terrible  poisons,  a  few 
drops  producing  death  in  a  few  seconds  ;  and  even  its 
vapor,  largely  diluted  with  air,  brings  on  very  unpleasant 
symptoms.  Under  the  action  of  strong  acids  it  is  decom- 
posed into  ammonia  and  formic  acid,  the  change  being 
very  simple  : 

C>N,  H  +  3 HO  =  NH3  +  C.2HOS. 

Under  such  circumstances,  hydrochloric  acid  yields  mu 
riate  of  ammonia  and  hydrated  formic  acid.  Hydrocy 
anic  acid  may,  to  a  certain  extent,  be  preserved  from 
spontaneous  change  by  the  presence  of  a  minute  quantity 
of  any  mineral  acid. 

Prussic  acid  may  be  detected  by  its  smell,  and  by  yield- 
ing a  precipitate  of  Prussian  blue  when  acted  upon  in  so- 
lution successively  by  sulphate  of  iron,  potash,  and  an  ex- 
cess of  hydrochloric  acid.  The  liquid  in  which  the  poison 
is  suspected  to  exist  should  be  acidulated  with  sulphuric 
acid  and  distilled,  and  the  hydrocyanic  acid  will  be  found 
in  the  first  portions  which  come  over. 

Amygdaline  (C4()H^NO.22). — A  crystallizable  substance 
found  in  bitter  almonds,  the  kernels  of  peaches,  &c. ;  is  of 
considerable  interest  in  connection  with  hydrocyanic  acid, 
inasmuch  as  these  organic  bodies  yield,  when  distilled  with 
water,  that  substance.  The  change  consists  in  the  ac- 
tion of  water  upon  amygdaline  by  the  aid  of  an  azotized 
ferment  called  Synaptase,  or  Emulsine,  which  constitutes 
the  larger  portion  of  the  pulp  of  almonds ;  the  bitter  al- 
mond oil  at  the  same  time  makes  its  appearance.  Amyg- 
daline may  be  abstracted  from  the  paste  of  bitter  almonds, 
from  which  the  fixed  oil  has  been  expressed,  by  the  aid 
of  boiling  alcohol,  which  being  subsequently  distilled  off, 
the  sugar  which  is  contained  in  the  sirupy  residue  is  de- 
stroyed by  fermentation  with  yeast.  The  liquid  being 

What  are  its  properties  ?  What  is  the  action  of  strong  acids  upon  it  ? 
How  may  it  be  partially  preserved  from  spontaneous  change  ?  How  may 
it  be  detected  ?  What  is  amygdaline  ?  What  is  tke  potion  of  aynaptase 
and  water  upon  it  ?  How  may  it  be  obtained  ? 


COMPOUNDS  OF  CYANOGEN.  353 

evaporated  again  to  a  sirup,  is  mixed  with  alcohol,  which 
precipitates  the  amygdaline  as  a  white  crystalline  pow- 
der, purified  by  being  redissolved  in  alcohol  and  left  to 
cool.  It  is  soluble  in  hot  and  cold  water,  but  sparingly 
soluble  in  cold  alcohol.  A  weak  solution  of  it  in  water, 
under  the  influence  of  a  small  quantity  of  the  emulsion  of 
sweet  almonds,  yields  at  once  oil  of  bitter  almonds  and 
hydrocyanic  acid.  When  amygdaline  is  boiled  with  an 
alkali,  it  yields  Amygdalinic  Acid,  which  forms  a  salt  with 
the  alkali,  and  ammonia  is  evolved. 

Cyanide  of  Potassium  (KCy)  may  be  formed  by  the  di- 
rect union  of  cyanogen  and  potassium,  or  by  the  ignition 
of  the  ferrocyanide  of  potassium  in  a  close  vessel.  For 
common  purposes  in  the  arts  it  may  be  formed  in  a  state 
somewhat  impure  by  mixing  eight  parts  of  ferrocyanide 
of  potassium,  rendered  anhydrous  by  heat,  with  three  of 
carbonate  of  potash,  also  dry,  and  fusing  the  mixture  in  a 
crucible,  stirring  it  until  the  fluid  part  of  the  mass  is  col- 
orless. The  sediment  is  allowed  to  settle,  and  the  clear 
liquid  poured  off;  it  is  the  substance  in  question.  Cyanide 
of  potassium  is  very  soluble  in  water,  yields  colorless  oc- 
tahedral crystals,  which  deliquesce  in  the  air;  it  melts 
without  change  at  a  red  heat,  and  exhales  the  odor  of 
prussic  acid.  It  is  very  poisonous. 

Cyanide  of  Mercury  may  be  made  by  dissolving  red 
oxide  of  mercury  in  hydrocyanic  acid,  or  by  the  action  of 
a  solution  of  ferrocyanide  of  potassium  on  sulphate  of 
mercury ;  the  cyanide  crystallizing  from  the  filtered  hot 
solution.  It  forms  fine  prismatic  crystals,  more  soluble  in 
hot  than  cold  water.  It  is  poisonous  ;  and,  when  decom- 
posed at  a  low  red  heat,  yields  cyanogen  gas. 

Cyanic  Acid(CyO-\-HO)  is  procured  by  heating  in  a  re- 
tort cyanuric  acid,  deprived  of  its  water  of  crystallization ; 
a  colorless  liquid  comes  over  into  the  receiver,  which  is 
the  hydrated  cyanic  acid ;  it  has  a  strong  odor  like  acetic 
acid,  and  produces  blisters  on  the  skin.  It  is  decomposed 
by  the  contact  with  water  into  bicarbonate  of  ammonia. 

C2NO,  HO  +  2HO  ...  =  ...  C2O4  +  NH3, 
and  is  a  very  instable  body,  spontaneously  changing  in  a 
short  time  into  Cyamelide,  a  body  of  the  same  constitu- 

By  what  processes  may  the  cyanide  of  potassium  be  made  ?     How  may 
the  cyanide  of  mercury  be  prepared?    Exposed  to  heat,  what  does  it 
yield  ?    What  are  the  constitution  and  properties^  of  cyanic  acid  ? 
G  o2 


364  DERIVATIVES    OF    CYANOGEN. 

tion,  but  a  white  opaque  solid,  insoluble  in  water  and  al- 
cohol, and  decomposed  by  hot  oil  of  vitriol  into  carbonate 
of  ammonia. 

Fulminic  Acid  (Ci/2O2-\-2HO)  has  not  yet  been  insula- 
ted, but  some  of  its  salts,  presently  to  be  described,  are 
characterized  by  the  violence  with  which  they  detonate 
under  very  trivial  disturbances.  It  is  a  bibasic  acid. 

Cyanuric  Acid(Cy3Os+3HO)  may  be  made  by  heating 
urea,  which  disengages  ammonia ;  the  residue  is  dissolved 
in  hot  sulphuric  acid,  and  nitric  acid  added  until  the 
liquid  becomes  colorless  :  on  mixing  it  with  water,  and 
allowing  it  to  cool,  the  cyanuric  acid  separates.  Its  crys- 
tals are  efflorescent ;  it  is  sparingly  soluble  in  water,  and  is 
a  tribasic  acid ;  and,  as  has  been  already  stated,  at  a  red 
heat  it  may  be  distilled,  and  yields  cyanic  acid  without 
other  product. 


LECTURE  LXXIX. 

BODIES  ALLIED  TO  CYANOGEN. — Salts  of  the  Oxycyano- 
gen  Acids. — FERROCYANOGEN. —  Ferrocyanides  of  Hy- 
drogen and  Potassium. — Prussian  Blue  and  Basic  Blue. 
— FERRIDCYANOGEN. — SULPHOCYANOGEN. — Compounds 
with  Hydrog-en  and  Potassium. — Melam,  Melamine,  Sfc. 

CYANATE  of  Potash  (KO,  CyO]  maybe  prepared  by  ox- 
ydizing  cyanide  of  potassium  by  oxide  of  lead  in  an  earth- 
en crucible  ;  the  result  boiled  with  alcohol  yields,  on  cool- 
ing, crystals  of  cyanate  of  potash,  in  thin,  transparent 
plates,  which  undergo  no  change  in  dry  air,  but  with 
moisture  become  converted  into  bicarbonate  of  potash 
and  ammonia. 

Cyanate  of  Ammoniac-Urea  (C2H4N2O^). — The  vapor 
of  hydrated  cyanic  acid,  mixed  with  ammoniacal  gas, 
yields  cyanate  of  ammonia.  The  solution  in  water,  when 
heated,  gives  off  ammonia,  and  the  cyanate  changes  into 
Urea,  from  which  caustic  alkalies  can  not  disengage  am- 
monia. Urea  may  also  be  made  from  the  action  of  sul- 
phate of  ammonia  or  cyanate  of  potash. 

What  of  fulminic  acid  ?     What  of  cyanuric  acid  ?     How  is  the  cyanate 
of  potash  made  ?     How  may  urea  be  formed  artificially  ? 


SALTS  OF  FULMINIC  ACID.  355 

Fulminate  of  Silver  (2AgO,  C4N.2O.2)  is  made  by  dis- 
solving silver  in  warm  nitric  acid  and  adding  alcohol.  It 
separates  from  the  hot  liquid  in  white  grains,  which,  being 
washed  in  water,  are  dried  in  small  portions  on  filtering 
paper.  It  detonates  with  wonderful  violence  when  ei- 
ther struck  or  rubbed.  It  is  sparingly  soluble  in  hot  wa- 
ter, and  crystallizes  from  that  solution  on  cooling.  It 
yields,  by  digestion  with  water  and  metals,  salts,  as  those 
of  zinc  and  copper. 

Fulminate  of  Mercury  (2HgO,  CtN2O.2)  is  prepared  in 
the  same  manner  as  the  foregoing,  and,  like  it,  is  very  ex- 
plosive. It  is  used  for  making  percussion  caps. 

Chloride  of  Cyanogen  (CyCl)  is  prepared  by  the  action 
of  chlorine  on  moist  cyanide  of  mercury  in  the  dark.  It 
is  a  colorless  gas,  soluble  in  water,  congeals  at  0°,  and 
boils  at  11°  ;  condenses  into  a  liquid  under  the  pressure 
of  four  atmospheres.  When  kept  in  this  condition,  in 
sealed  tubes,  for  a  length  of  time,  it  assumes  the  solid 
state,  which  form  may  also  be  given  to  it  by  acting  on  an- 
hydrous hydrocyanic  acid  by  chlorine  in  the  sun's  rays ; 
hydrochloric  acid  is  formed,  and  the  solid  cyanide  crys- 
tallizes. It  exhales  a  peculiar  odor,  melts  at  284°,  and 
is  soluble  in  alcohol  and  ether. 

FERROCYANOGEN. 

Ferrocyanogen  (C6N3Fe  =  Cfy)  is  an  ideal  compound 
radical. 

Hydroferrocyanic  Acid  (Cfy,  2H)  may  be  obtained  by 
decomposing  the  insoluble  ferrocyanide  of  lead  by  sul- 
phureted  hydrogen  while  suspended  in  water.  The  so- 
lution being  filtered,  is  to  be  evaporated  with  sulphuric 
acid  in  vacuo  until  the  acid  is  left  solid.  It  may  also  be 
prepared  by  agitating  its  aqueous  solution  with  ether,  or 
by  adding  hydrochloric  acid  to  a  strong  solution  of  ferro- 
cyanide of  potassium,  and  then  mixing  it  with  ether,  which 
precipitates  the  acid.  It  is  soluble  in  water,  to  which  it 
gives  a  powerful  acid  reaction.  It  decomposes  alkaline 
carbonates  with  effervescence,  and  does  not  dissolve  ox- 
ide of  mercury  in  the  cold.  In  these  respects,  therefore, 
it  strikingly  differs  from  hydrocyanic  acid. 

What  is  the  process  for  preparing  fulminating  silver,  and  what  are  ita 
properties  1  For  what  purpose  is  fulminate  of  mercury  used  ?  What  re- 
sults from  the  action  of  chlorine  on  cyanide  of  mercury  in  the  dark  ?  What 
te  ferrocyanogen  ?  How  is  hydroferrocyanic  acid  obtained  ? 


356  COMPOUNDS    OF    FERROCYANOGEN. 

Ferrocyanide  of  Potassium  —  Prussiate  of  Potash  — 
(2K,  Cfy+  3HO).  —  This  salt  is  made  on  the  large  scale  by 
igniting  potash,  iron  filings,  and  animal  matters  in  an  iron 
vessel;  the  mass  is  then  acted  upon  by  hot  water,  which  dis- 
solves out  a  large  quantity  of  cyanide  of  potassium,  which 
is  converted  into  the  ferrocyanide  by  the  iron,  and  the 
filtered  solution,  on  cooling,  yields  it  in  lemon-colored 
crystals,  soluble  in  four  parts  of  cold  water.  It  is  not 
poisonous.  At  a  red  heat  it  decomposes,  and  yields  cy- 
anide of  potassium.  It  is  a  very  valuable  reagent  ;  with 
copper  it  yields  a  chocolate  precipitate  ;  with  protoxide 
of  iron,  a  white  ;  and  with  peroxide  of  iron,  Prussian  blue. 

Common  Prussian  Blue  (3  Cfy  +  4  Fe)  is  prepared  by 
precipitating  a  persalt  of  iron  by  solution  of  ferrocyanide  of 
potassium  ;  when  dry,  it  is  of  a  deep  blue,  with  a  lustre  of 
coppery-red.  It  is  insoluble  in  water,  is  decomposed  by 
alkaline  solutions,  which  yield  alkaline  ferrocyanides,  and 
precipitate  oxide  of  iron.  It  is  soluble  in  solution  of  ox- 
alic acid,  and  then  constitutes  the  basis  of  blue  writing 
inks,  which  are  used  for  steel  pens.  It  is  also  much  em- 
ployed as  a  paint. 

Basic  Prussian  Blue  (3Cfy,  kFe  +  FeO.j)  is  formed  when 
the  white  precipitate,  yielded  by  a  protosalt  of  iron  with 
ferrocyanide  of  potassium,  is  exposed  to  the  air.  As  its 
formula  shows,  it  is  common  Prussian  blue,  with  perox- 
ide of  iron.  It  differs  from  Prussian  blue  in  the  remark- 
able peculiarity  that  it  is  soluble  in  pure  water. 

FERRIDCYANOGEN. 

Ferridcyanogen  (C12N6Fe.2  =  Cfdy}.  —  A  hypothetical 
compound  radical,  which  yields  some  compounds  of  in- 
terest. 

Ferridcyanide  of  Potassium  (3J£  -f-  Cfdy)  may  be  made 
by  passing  chlorine  through  a  dilute  solution  of  ferrocy- 
anide of  potassium  until  it  ceases  to  yield  a  precipitate 
with  a  persalt  of  iron.  The  liquid  being  concentrated, 
yields,  on  cooling,  deep-red  crystals,  the  solution  of  which 
is  of  a  greenish  color.  It  gives  no  precipitate  with  perox- 
ide of  iron,  but  with  the  protosalts  a  bright  blue,  lighter 
than  Prussian  blue,  and  known  as  Turnbull's  Blue. 


How  is  the  prussiate  of  potash  prepared  ?  Is  it  poisonous  ?  What  color 
does  it  give  with  protoxide  and  peroxide  of  iron?  What  is  common 
Prussian  blue  ?  What  is  its  composition  ?  For  what  purposes  is  it  use-'  7 
In  what  respect  does  basic  Prussian  blue  differ  from  it  ?  What  is  the  c** 


SULPHOCYANOGEN.  357 

Cobaltocyanogen,  a  hypothetical  radical,  yielding  com- 
pounds analogous  to  the  preceding  bodies. 

Sulphocyanogen  (C.2NS.2)  (Csy),  a  compound  radical,  not 
yet  insulated  with  certainty.  Its  formula  shows  that  it  is 
a  bisulphuret  of  cyanogen. 

HydrosulpJiocyanic  Acid  (CsyH]  may  be  obtained  by 
decomposing  sulphocyanide  of  lead  by  sulphureted  hy- 
drogen in  water.  The  solution  is  decomposed  by  ebulli- 
tion. It  has  the  odor  of  acetic  acid.  It  yields  with  per- 
oxide of  iron  a  blood-red  color. 

Sulphocyanide  of  Potassium  (KCsy)  may  be  made  by 
heating  powdered  ferrocyanide  of  potassium  with  half  its 
weight  of  sulphur  and  Dne  third  of  carbonate  of  potash, 
and  keeping  it  melted  for  a  short  time.  The  mass  is  then 
boiled  with  water,  which  dissolves  out  the  sulphocyanide, 
and  the  solution  being  concentrated,  yields  prismatic  crys- 
tals of  the  salt.  It  is  soluble  in  water  and  alcohol,  and 
deliquesces  in  the  air.  It  melts  at  a  red  heat.  Its  solu- 
tion with  peroxide  of  iron  yields  a  blood-red  color. 

Mclam  (C^HgNu)  is  produced  when  sulphocyanide  of 
ammonium  is  distilled  at  a  high  temperature,  or  by  heating 
dry  sulphocyanide  of  potassium  with  twice  its  weight  of 
sal  ammoniac.  It  is  insoluble  in  water,  but  dissolves  in 
strong  sulphuric  acid.  When  heated,  it  yields  mellone 
and  ammonia. 

Melamine  (C6H6Ne)  is  produced  when  melam  is  dissolv- 
ed in  a  hot  solution  of  potash.  It  separates  on  cooling. 
It  is  a  basic  body,  uniting  with  acids. 

Ammeline  (CjfiZ^O.J  remains  in  the  solution  after  the 
melamine  has  crystallized.  It  may  be  precipitated  with 
acetic  acid. 

Ammelide  (Cl2JH~9iV906)  is  prepared  by  dissolving  amine- 
line  in  sulphuric  acid,  and  precipitating  with  alcohol. 

What  are  cobaltocyanogen  and  sulphocyanogen?  What  color  does 
hydrosulphocyanic  acid  yield  with  peroxide  of  iron  ?  By  what  process  is 
sulphocyanide  of  potassium  made  ?  What  results  from  the  distillation  Df 
the  sulphocyanide  of  ammonium  1  What  are  melamine,  ammeline,  and 
ammelide  ? 


358  MELLONE. 


LECTURE  LXXX. 

MELLONE  —  UREA.  —  Mellone,  Preparation  of.  —  Mellomdes 
of  Hydrogen  and  Potassium.  —  Natural  and  artificial 
Formation  of  Urea.  —  Uric  Acid.  —  Its  Properties.  —  De- 
rivatives of  Uric  Acid.  —  Parabanic,  Oxaluric,  and  Thi- 
onuric  Acids.  —  Alloxantine.  —  Purpurate  of  Ammonia.— 
Xanthic  and  Cystic  Oxides. 


MELLONE  (C6N^  =Me).  —  If  sulphocyanideof  potassium 
be  acted  upon  by  chlorine  or  nitric  acid,  a  yellow  pow- 
der is  deposited  ;  this,  when  heated,  gives  off  bisulphuret 
of  carbon  and  sulphur,  and  there  is  left  a  yellowish  pow- 
der, which  is  mellone.  The  relation  of  its  constitution 
with  cyanogen  is  obvious.  It  resists  a  moderate  heat  with- 
out change. 

Hydromellonic  Acid  (  MeH  ).  —  By  adding  hydrochloric 
acid  to  a  hot  solution  of  mellonide  of  potassium,  this  acid 
separates  as  a  white  powder  on  cooling.  It  is  partially 
soluble  in  hot  water,  and  possesses  strong  acid  powers. 

Mellonide  of  "Potassium  (KMe)  maybe  prepared  by  melt- 
ing ferrocyanide  of  potassium  with  half  its  weight  of  sul- 
phur, and  adding,  when  the  fusion  is  complete,  five  per 
cent,  of  dry  carbonate  of  potash.  The  resulting  mass  is 
acted  on  by  water,  and  the  solution  being  filtered,  is  evap- 
orated, until,  on  cooling,  it  forms  a  mass  of  crystals,  from 
which  the  sulphocyanide  may  be  removed  by  alcohol,  and 
the  mellonide  left.  It  is  soluble  in  water,  and  yields,  by 
double  decomposition  with  the  salts  of  baryta,  lime,  &c., 
mellonides  of  these  bodies,  for  the  most  part  sparingly 
soluble. 

Urea  (C2HtN2O^)  may  be  obtained  from  urine  by  add- 
ing to  it,  when  concentrated,  a  strong  solution  of  oxalic 
acid.  The  precipitated  oxalate  of  urea  is  to  be  boiled 
with  powdered  chalk,  arid  the  filtered  solution  concentra- 
ted until  the  urea  crystallizes  on  cooling.  It  may  also  be 
made  artificially  by  adding  to  a  strong  solution  of  cyanate 
of  potash  an  equal  ^weight  of  dry  sulphate  of  ammonia  ; 
the  solution  is  evaporated  to  dryness  in  a  water  bath,  and 

How  is  mellone  prepared  ?  What  is  the  action  of  hydrochloric  acid  on 
the  mellonide  of  potassium  1  How  may  urea  be  made  artificially  ? 


URIC    ACID.  359 

the  urea  dissolved  out  by  alcohol.  It  crystallizes  in  prisms, 
very  soluble  in  water,  but  permanent  in  the  air.  At  a 
high  temperature  it  gives  off  ammonia  and  cyanate  of^ 
ammonia,  cyanuric  acid  remaining.  Urea  contains  the  ele- 
ments of  cyanate  of  oxide  of  ammonium,  has  neither  an 
acid  nor  alkaline  reaction,  is  decomposed  by  hot  alkaline 
solutions,  with  evolution  of  ammonia,  and,  by  uniting  with 
two  atoms  of  water,  yields  carbonate  of  ammonia,  a  result 
which  takes  place  during  the  putrefaction  of  urine,  the 
change  being  brought  on  by  a  nitrogenized  ferment — 
the  mucus  of  the  bladder.  Urea  unites  with  acids,  and 
forms,  with  nitric  and  oxalic  acids,  characteristic  salts. 

Uric  Acid — Lithic  Acid  ( CIQH4N4O6) — may  be  obtained 
from  the  solid  urine  of  serpents,  which,  being  boiled  in 
solution  of  caustic  potash  and  filtered,  yields  uric  acid,  by 
the  addition  of'hydrochloric  acid,  as  a  white,  inodorous,  and 
sparingly  soluble  powder ;  soluble  without  change  in  sul- 
phuric acid,  from  which  it  is  precipitated  by  water.  Uric 
acid  also  exists  in  human  urine,  and  appears  to  be  always 
a  product  of  the  action  of  the  animal  economy.  Of  its  salts, 
the  urate  of  soda  is  interesting ;  it  is  the  chief  ingredient 
of  gouty  concretions  in  the  joints,  called  chalk-stones. 
The  urate  of  ammonia  occurs  as  a  urinary  calculus,  and 
is  often  deposited  from  urine  as  a  reddish  cloud  or  pow- 
der. 

Allantoin  (C4H3N2O3)  is  prepared  by  boiling  uric  acid 
with  peroxide  of  lead ;  the  filtered  solution,  being  con- 
centrated, deposits  prismatic  crystals  of  allantoin  on  cool- 
ing. It  is  soluble  in  160  parts  of  cold  water.  By  a  solu- 
tion of  caustic  alkali  it  is  decomposed  into  ammonia  and 
oxalic  acid,  assuming,  during  this  change,  the  elements 
of  three  atoms  of  water. 

Alloxan  (CSH4N.2O10)  is  made  by  the  action  of  concen- 
trated nitric  acid  on  uric  acid  in  the  cold.  The  uric  acid 
is  to  be  added  in  small  portions  successively,  until  about 
one  third  the  weight  of  the  nitric  acid  has  been  used.  An 
effervescence  takes  place,  and  there  is  left  a  white  mass, 
from  which  the  excess  of  acid  is  to  be  drained.  The  sub- 
stance is  then  to  be  dissolved  in  hot  water  and  crystallized. 

What  are  its  properties  ?  To  what  substance  does  it  give  rise  in  fer- 
mentation ?  Under  what  circumstances  does  uric  acid  occur  1  What  are 
jhalk-stones  ?  Under  what  form  does  urate  of  ammonia  occur  ?  How 
may  allantoin  be  prepared  ?  What  is  the  action  of  cold  nitric  acid  on  urio 
acid  ? 


360  '   ALLOXANIC    ACID. 

Its  solution  has  an  acid  reaction  and  a  bitter  taste,  and 
stains  the  skin  purple,  and,  with  a  protosalt  of  iron  and  an 
Alkali,  yields  a  characteristic  blue  compound. 

Alloxanic  Acid  ( C4HNO4  +  HO)  may  be  prepared  by 
decomposing  the  alloxanate  of  baryta  by  dilute  sulphuric 
acid.  The  alloxanate  itself  is  obtained  by  the  addition 
of  barytic  water  to  a  warm  solution  of  alloxan.  It  is  a 
strong  acid,  decomposing  carbonates,  and  even  water,  by 
the  aid  of  zinc. 

Mesoxalic  Acid  (C3O4  -f  2 HO). — Mesoxalic  acid  may 
be  obtained  by  boiling  a  solution  of  alloxan  with  acetate 
of  lead,  the  resulting  mesoxalate  of  lead  being  decom- 
posed by  sulphureted  hydrogen.  It  is  a  strong  acid,  re- 
sists a  boiling  heat,  and  is  bibasic. 

Mykomelinic  Acid  (CsHdN4O5)  is  prepared  by  boiling  a 
solution  of  alloxan  with  an  excess  of  ammonia,  and  then 
precipitating  by  an  excess  of  dilute  sulphuric  acid.  It  is 
a  light  yellow  powder. 

Parabanic  Acid  (C6N3O4  +  2HO)  is  formed  by  the  ac- 
tion of  strong  nitric  acid  on  alloxan,  or  uric  acid,  by  the 
aid  of  heat.  The  crystals  form  on  cooling,  and  may  be 
dried  by  draining,  and  then  recrystallized.  It  is  soluble 
in  water,  reddens  litmus,  and  forms  beautiful  prismatic 
crystals. 

Oxaluric  Acid  (C6H3N.2O7  -f  HO)  may  be  made  by  de- 
composing a  hot  solution  of  the  oxalurate'  of  ammonia  by 
dilute  sulphuric  acid,  and  cooling  rapidly.  The  ammonia 
salt  is  itself  procured  by  boiling  a  solution  of  the  para- 
banate  of  ammonia,  when  it  crystallizes,  on  cooling,  in 
small  needles.  Oxaluric  acid  is  a  white  crystalline  pow- 
der ;  it  contains  the  elements  of  one  atom  of  parabanic 
acid  and  three  of  water,  and  its  solution,  by  boiling,  yields 
oxalic  acid  and  oxalate  of  urea. 

Thionuric  Acid  (CsH&N&Olt  +  2HO),  a  bibasic  acid 
prepared  by  decomposing  thionurate  of  lead  with  sul- 
phureted hydrogen.  It  contains  the  elements  of  one  atom 
of  alloxan,  one  of  ammonia,  and  two  of  sulphurous  acid. 

Uramile  (CSH5N3O6). — When  an  excess  of  a  saturated 
solution  of  sulphurous  acid  in  water  is  mixed  with  a  cold 

How  is  alloxanic  acid  prepared  ?  What  substance  results  from  boiling 
alloxan  with  acetate  of  lead  ?  How  is  mykomelinic  acid  prepared  ? 
What  substance  results  from  the  action  of  hot  nitric  acid  on  ui-ic  acid  ? 
What  is  the  relation  between  oxaluric  and  parabanic  acid?  How  is 
uramile  prepared  ? 


ALLOXANTINE. MUREXIDE.  361 

solution  of  alloxan,  and  an  excess  of  carbonate  of  ammo- 
nia with  caustic  ammonia  added,  and  the  whole  boiled, 
the  thionurate  of  ammonia  is  deposited  on  cooling.  From 
this  the  lead  salt,  used  in  the  preparation  of  the  foregoing 
acid,  may  be  obtained  by  acetate  of  lead.  The  thionurate 
of  ammonia,  with  a  little  hydrochloric  acid,  being  boiled 
in  a  flask,  there  separates  a  white  body,  which  is  uramile. 
It  differs  from  thionuric  acid  in  not  containing  the  ele- 
ments of  two  atoms  of  sulphuric  acid.  If  the  thionurate 
of  ammonia  is  mixed  with  dilute  sulphuric  acid  and  evap- 
orated in  a  water  bath,  Uramilic  Acid  is  deposited  ;  it  is 
CIGH10N,015. 

Alloxantine  (CsH5N2Om)  is  made  when  sulphureied 
hydrogen  gas  is  passed  through  a  cold  solution  of  alloxan. 
The  product  is  filtered,  washed,  and  boiled  in  water, 
which  deposits  the  alloxantine,  on  cooling,  in  transparent 
rhombic  prisms,  which  turn  red  on  exposure  to  ammonia. 
This  substance  is  alloxan,  with  one  atom  of  hydrogen.  A 
hot  solution  of  it  is  decomposed  when  a  stream  of  sulphur- 
eted  hydrogen  is  passed  through  it,  and  Dialuric  Acid 
forms. 

Murexide — Purpuratc  of  Ammonia  (C^H6NbOg) — may 
be  made  by  the  action  of  dilute  nitric  acid  on  uric  acid, 
and  then  adding  ammonia,  or  by  boiling  equaj  weights  of 
uramile  and  red  oxide  of  mercury  with  eighty  times  their 
weight  of  water^  rendered  alkaline  by  ammonia.  The 
liquid  turns  of  a  deep  purple  color,  and,  when  filtered, 
deposits,  on  cooling,  crystals  of  murexide  in  square 
prisms,  which,  by  reflected  light,  are  of  a  green  metallic 
lustre,  and,  by  transmitted  light,  of  a  purple.  It  is  spar- 
ingly soluble  in  cold  water,  but  much  more  so  in  hot,  and 
is  one  of  the  most  splendid  compounds  known. 

Murexan — Purpuric  Acid. — Murexide  is  to  be  dissolved 
in  a  solution  of  caustic  potash,  and  dilute  sulphuric  acid 
added.  It  forms  a  yellow  powder,  and,  dissolved  in  am- 
monia, gives  rise  to  the  foregoing  body.- 

Xantkic  Oxide  (C4HyN2O2)  occurs  as  a  urinary  calculus 
of  a  brown  color  and  waxy  aspect.  The  calculus  may 
be  dissolved  in  dilute  potash,  and  xanthic  oxide  precipi- 

How  is  alloxantine  prepared  ?  What  is  tlie  action  of  dilute  nitric  acid 
and  ammonia  on  uric  acid '/  What  is  the  color  of  the  crystals  of  murexjde  ? 
How  may  murexan  be  prepared  ?  Under  what  circumstances  dp  xanthjo 
oxide  mid  cystic  oxide  occur  ? 

H  H 


362  THE     VEUETAliLE    AClUd. 

tates  as  a  white  powder  by  carbonic  acid.     It  is  a  waxy 
body. 

Cystic   Oxide  (C6Hf,NS^O4)  occurs  also   as  a  urinary 
calculus. 


LECTURE  LXXXI. 

TIJE  VEGETABLE  ACIDS.—  Tartaric  Acid,  Preparation 
of.  —  Salts  of  Tartaric  Acid.  —  Acids  allied  to  Tartar- 
ic.  —  Citric  and  its  allied  Acids.  -*-Malic  and  its  allied 
Acids.  —  Tannic  Acid.  —  Gallic  Acid.  —  Acicts  allied  to 
them. 

OF  the  vegetable  acids  several  will  be  described  with 
Jheir  associated  alkalies.  The  following  are  those  of 
which  I  shall  treat  in  this  Lecture  : 


Tartaric.    .........  Cs  H*OW  -f-  2HO. 

Paratartaric     ......  .  .  C%  H*QW  -f-  '2HO. 

Pyrotartarie     .     ....    .     .     .  Cn  H.,O->   +    HO 

Tartralic      .......      26's  H^Oio  -f  3HO 

Tartrelic      ........  CsH4O10--    HO. 

.Citric       .....     ...     .  jCi2H-,Oll--3HO. 

Aconitrc  .......    .    .  C4  H  O3  -  -   HO. 

Malic  ..........  Gs  H*Os  4-  %HO. 

Maleic     ..........  CsHiOs  --2ffO. 

Fuiriavk  r  -    .    -   V    •    •    .    .  C4  H  Oa   -f    HO. 
Tannic    .....     .     .     .     .  Cis/ftOo   -f  3HO. 

Gallic      .........  Ci  H  O3  -)-  1HO. 

Ellagic    ....:....  Ci  H2O4. 

Pyrogallic   .......    .  CQ  HzOs. 

-MetagaUic  .......    .  CQ  HzO*. 

Besides  acids  such  as  these,  which  constitute  a  very  nu- 
merous group,  there  is  another  class,  which  pass  under 
the  name  of  Coupled  Acids,  the  peculiarity  of  which  is,  that 
they  consist  of  an  acid  affixed  or  coupled  to  another  body, 
which,  without  affecting  the  neutralizing  power  of  the 
acid,  accompanies  it  in  all  its  combinations.  Thus,  hypo- 
sulphuric  acid  couples  with  naphthaline  to  form  hyposul- 
phonaphthalic  acid,  which  neutralizes  just  as  much  of  any 
base  as  hyposulphuric  acid  itself  could  do,  the  naphtha- 
line not  changing  its  powers. 

Tartaric  Acid  (CSH4OK  +  2HO}.  —  A  bibasic  acid  which 

occurs,  as  has  been  already  stated,  in  the  juice  of  grapes 

and  other  fruits  as  bitartrate  of  potash.     It  may  be  ob- 

tained by  dissolving  cream  of  tartar  in  boiling  water  and 

What  are  coupled  acids  ?     From  what  source  is  tartarie  acid  derived  ? 


SALTS    OF    TARTARIC    ACID.  363 

adding  powdered  chalk,  a  tartrate  of  lime  precipitating. 
The  rest  of  the  tartaric  acid  may  be  obtained  from  the  so- 
lution by  the  addition  of  chloride  of  calcium,  which  yields 
another  portion  of  tartrate  of  lime,  which  may  be  decom- 
posed by  digesting  with  an  equivalent  proportion  of  dilute 
sulphuric  acid.  The  concentrated  and  filtered  solution 
yields  crystals  acid  to  the  taste,  inodorous,  and  soluble 
both  in  water  and  alcohol ;  the  solution  decomposes  by 
keeping.  '*  Tartaric  acid  yields  several  valuable  salts. 

Tartrate  of  Potash— Soluble  Tartar  (2KO,  CSH4O10)— 
may  be  made  by  adding  carbonate  of  potash  to  cream  of 
tartar.  It  is  very  soluble. 

Bitartrate  of  Potash — Cream  of  Tartar  (KO,  HO, 
C.H+Oio). — This  is  the  salt  which  is  deposited  from  the 
juice  of  the  grape  during  fermentation,  as  Argol.  It  may 
be  purified  from  the  coloring  matter  it  contains  by  solution 
in  hot  water,  and  the  action  of  animal  charcoal.  In  cold 
water  it  is  very  sparingly  soluble.  It  yields  black  flux 
when  ignited  in  a  close  vessel,  the  black  flux  being  car- 
bonate of  potash  enveloped  in  carbonaceous  matter. 

Tartrate  of  Potash  and  Soda — Rochelle  Salt — Salt  oj 
Seignette  (KO,  Na  O,  C,H^  O10  -f  1  OHO)— may  be  procured 
by  neutralizing  a  solution  of  the  foregoing  salt  with  car- 
bonate of  soda.  On  evaporation  and  cooling  it  separates 
in  large,  prismatic  crystals. 

Tartrate  of  Antimony  and  Potash —  Tartar  Emetic 
(KOSb,O,,  C,H,Oi0-\-2HOy.—This  valuable  medicinal 
agent  is  made  by  boiling  oxide  of  antimony  with  a  solu- 
tion of  cream  of  tartar ;  on  cooling,  the  crystals  are  depos- 
ited. They  are  much  more  soluble  in  hot  than  in  cold 
water,  and  dissolve  without  decomposition. 

Racemic  Acid — Paratartaric  Acid. — This  remarkable 
acid,  which  has  the  same  constitution  as  tartaric  acid,  and 
resembles  it  very  closely,  is  found  in  the  grapes  of  certain 
parts  of  Germany  and  France.  Racemic  acid,  however, 
differs  from  tartaric  in  yielding  a  precipitate  with  a  neu- 
tral salt  of  lime. 

Pyrotartaric  Acid  (C6H3O6+  HO)  is  obtained  by  the 
destructive  distillation  of  tartaric  acid,  coming  over  with 
a  variety  of  other  products. 

What  is  soluble  tartar  ?  From -what  source  is  cream  of  tartar  derived? 
What  is  Roehslle  salt  ?  How  is  tarta>-  emetic  prepared  ?  What  is  the 
relation  between  racemic  and  tartaric  acids  ? 


364  CITRIC  ACID. 

The  action  of  heat  on  tartaric  acid  is  remarkable.  When 
exposed  to  a  temperature  of  400°  F.,  it  melts,  throws  off 
water,  and  yields  in  succession  three  different  acids,  tar- 
tralic,  tartrelic,  and  anhydrous  tartaric  acid,  the  constitu- 
tion of  which,  compared  with  tartaric  acid,  is  as  follows  : 

Tartaric  acid CeH*Oi0 -\-2HO. 

Tartralic    " 2C8  #4  Oio -f  3HO. 

Tartrelic    " Ca  H^ Ow  +    HO. 

Anhydrous  tartaric CgH^Oio. 

All  these,  by  the  continued  contact  of  water,  pass  back 
into  the  condition  of  tartaric  acid. 

Citric  Acid  (Cl2H-,On-i-3HO),  a  tribasic  acid,  occurring 
abundantly  in  the  juice  of  lemons  and  other  sour  fruits, 
and  separated  therefrom  by  the  aid  of  chalk  and  sulphur- 
ic acid.  It  is  clarified  by  digestion  with  animal  charcoal, 
and  yields  prismatic  crystals  of  a  pleasant  taste,  and  sol- 
uble both  in  hot  and  cold  water.  The  crystals  are  of  two 
different  forms,  according  to  the  conditions  of  their  forma- 
tion ;  those  which  separate  in  the  cold  by  spontaneous 
evaporation  contain  five  atoms  of  water,  three  of  whicli 
are  basic ;  but  those  which  are  deposited  from  a  hot  solu- 
tion contain  only  four. 

The  citrates  form  a  very  numerous  family  of  salts,  for, 
as  the  acid  is  tribasic,  we  may  have  them  with  three  atoms 
of  metallic  oxide,  or  two  of  oxide  and  one  of  water,  or  one 
of  oxide  and  two  of  water,  besides  subsalts. 

AconiticAcid — EquiseticAcid(C4HOs  -f-  HO) — is  form- 
ed by  fusing  citric  acid,  and  the  resulting  brown  product 
is  dissolved  in  water,  the  change  being 

C»HS014  ...="...  3(  C<HOa)  +  5(J5TO), 
that  is,  one  atom  of  hydrated  citric  acid  yields  three  of 
aconitic  acid  and  five  of  water.     Aconitic  acid  is  remark- 
able from  occurring  naturally  in  the  Aconitum  Napellus  and 
Equisetum  Fluviatile. 

Malic  Acid  (C^H^O*  -f-  2HO),  a  bibasic  acid,,  occur- 
ring in  the  juice  of  apples  and  other  fruits.  It  may  also 
be  prepared  from  the  stalks  of  rhubarb,  in  which  it  occurs 
with  oxalate  of  potash.  It  is  a  colorless  solid,  soluble  in 
water,  the  solution  changing  by  keeping.  When  heated 
in  a  retort,  it  melts,  and  then  boils,  emitting  a  volatile 

Describe  the  action  of  heat  on  tartaric  acid.  From  what  source  is  citric 
acid  obtained  ?  How  many  classes  of  salts  does  citric  acid  yield  ?  What 
substance  results  from  the  fusion  of  citric  acid  ?  From  what  sources  is 
malic  acH  derived  ? 


TANNIC    ACID.  365 

acid,  the  MtJeic  Acid,  C8HZO6  +  2HO,  which  condenses 
with  the  water  in  the  receiver;  at  the  same  time  there 
forms  in  the  retort  crystalline  scales  of  Fumaric  Acid, 
C4HOt  +  H 0,  which  may  be  separated  from  the  unchang- 
ed malic  acid  by  solution  in  cold  water.  It  is  to  be  ob- 
served that  maleic,  fumaric,  and  aconitic  acids  are  isomer- 
ic  bodies. 

Tannie  Acid  ((718J9"5O9  -f  3HO). — An  astringent  princi- 
ple found  in  the  bark  of  the  oak,  nut-galls,  and  Fig.  272. 
other  vegetable  productions.  It  may  be  sep- 
arated by  placing  in  a  vessel,  Z>,  Fig.  272, 
powdered  galls.  On  pouring  on  them  sulphu- 
ric ether,  a  liquid  drops  through  the  funnel 
tube,  c,  into  the  bottle,  a,  spontaneously  sepa- 
rating into  two  portions ;  the  lower,  which  is 
a  solution  of  tannic  acid  in  water,  is  to  be  de- 
canted and  evaporated  in  presence  of  sul- 
phuric acid  in  vacuo.  It  yields  tannic  acid, 
or  tannin,  in  the  form  of  an  uncrystallized 
mass.  This  acid  is  soluble  in  water,  but  much 
less  so  in  ether,  has  an  astringent  taste,  and 
reddens  litmus  paper.  With  the  persalts  of 
iron  it  yields  a  characteristic  and  valuable  precipitate  of 
a  black  color,  the  basis  of  common  writing  ink.  It  forms 
insoluble  compounds  with  starch,  gelatine,  and  other  or- 
ganic bodies,  that  with  gelatine  being  of  considerable  in- 
terest. It  is  the  basis  of  leather.  From  the  characteris- 
tic precipitate  it  gives  with  that  metal,  it  is  used  as  a  test 
for  iron,  which  must,  however,  be  in  the  state  of  peroxide, 
as  the  protosalts  are  unacted  upon.  The  gradual  dark- 
ening of  pale  writing  inks  is  due  to  the  gradual  oxydation 
of  the  iron  they  contain. 

CatecMn  (Cl6Hti06). — There  is  a  body  extracted  by  hot 
water  from  catechu,  called  catechin.  It  crystallizes  in 
needles,  and  does  not  form  an  insoluble  compound  with 
gelatine,  and  gives  a  green  color  with  persalts  of  iron.  By 
the  action  of  caustic  potash  in  excess,  it  yields  a  black  and 
insoluble  substance,  Japonic  Acid.  By  the  action  of  car- 
bonate of  potash,  it  yields  Rubinic  Acid. 

What  two  acids  are  yielded  by  it  under  the  action  of  heat  ?  What  is 
the  relation  between  maleic,  fumaric,  and  aconitic  acids  ?  How  is  tan- 
nic acid  made  ?  What  color  does  it  yield  with  persalts  of  iron  ?  What  is 
the  basis  of  leather  ?  From  what  cause  do  pale  writing  inks  darken  ? 
What  is  catechin  ? 

H  H  2 


3t)8  GALLIC    ACID. 

Gallic  Acid  (C7HO3  -f  2HO)  may  be  formed  by  expos- 
ing a  solution  of  tannic  acid  J;o  the  air,  or  by  making 
powdered-  galls  into  a  paste  with  water,  and  keeping  it 
exposed  in  a  warm  place  to  the  air  for  some  weeks.  The 
mass  is  then  pressed  and  boiled  with  water.  On  cooling, 
the  solution  precipitates  a  quantity  of  gallic  acid,  which 
may  be  purified  by  re-crystallization.  Like  tannic  acid, 
this  substance  yields  no  precipitate  with  a  protosalt  of 
iron,  but  a  deep  blue-black  with  a  persalt.  It  does  not, 
however,  precipitate  gelatine.  Its  crystals  are  soluble  in 
one  hundred  parts  of  cold  and  three  parts  of  boiling  wa- 
ter. The  solution  has  an  astringent  taste. 

Tannic  acid  passes  into  gallic  acid  by  oxydation,  carbon- 
ic acid  and  water  being  evolved. 

08  ...  =  ...  2(C7H03  +  2HO)  +  2(HO) 


that  is,  one  atom  of  tannic  acid  and  eight  of  oxygen  yield 
two  of  gallic  acid,  two  of  water,  and  four  of  carbonic  acid. 

Ellagic  Acid  (C7H2O4)t  or  gallic  acid  minus  one  atom 
of  water,  may  be  extracted  after  the  removal  of  gallic  acid 
by  an  alkali,  and  precipitated  as  a  gray  powder  by  hydro- 
chloric acid. 

Pyrogallic  Acid  (C6H3O3)  sublimes  when  gallic  acid  is 
heated  in  a  retort  to  420°.  It  is  in  the  form  of  white  crys- 
tals, which  are  soluble  in  water.  It  strikes  a  black  color 
with  the  protosalts  of  iron. 

Metagallic  Acid  (C6Jf^O.2}  is  formed  when  gallic  acid  is 
suddenly  heated  in  a  retort  to  500°.  It  is  a  black  mass, 
insoluble  in  water,  but  soluble  in  alkalies,  from  which  it 
is  precipitated  as  a  black  powder  by  acids. 

How  may  gallic  acid  be  prepared?  How  is  ellagic  acid  procured? 
What  is  the  action  of  heat  on  allic  acid  ? 


VEGETABLE    ALKALIES.  367 


LECTURE  LXXXII. 

THE  VEGETABLE  ALKALIES. — General  Properties  of  Veg- 
etable Alkalies. — Morphia. — Its  Preparation  and  Prop- 
erties.—  Other  Alkalies  of  Opium. —  Meconic  Acid. — 
Alkalies  of  Bark,  Quina,  Cinchona,  fye. — Kinic  Acid. — 
Strychnia  and  Brucia. —  Table  of  Alkaloids. — Artificial 
Alkaloids. 

THE  vegetable  alkalies  constitute  an  extensive  class  of 
bodies,  which  are,  for  the  most  part,  the  active  medicinal 
agents  of  the  plants  in  which  they  occur.  They  are  gen- 
erally sparingly  soluble  in  water,  but  more  soluble  in 
boiling  alcohol,  of  a  bitter  taste,  and  characterized  by 
containing  nitrogen.  In  their  natural  state  they  are  unit- 
ed with  an  acid,  and,  possessing  basic  properties  in  a  very 
marked  manner,  neutralize  acids  completely.  This  qual- 
ity seems  to  depend  on  the  nitrogen  they  contain,  and 
has  no  reference  to  their  oxygen,  for  the  quantity  of  this 
latter  element  which  may  be  present  seems  to  have  no 
relation  to  their  neutralizing  power,  and,  indeed,  in  some 
of  them  it  is  not  present  at  all.  In  many  respects  they 
are  analogous  to  ammonia,  their  salts,  unlike  those  of 
some  of  the  compound  radicals,  such  as  ethyle,  &c.,  un- 
dergoing decomposition  in  the  same  manner  as  the  salts 
of  ammonia.  Thus,  the  chloride  of  ethyle  does  not  de- 
compose the  nitrate  of  silver,  but  the  analogous  com- 
pounds of  ammonia  and  the  vegetable  alkalies  do ;  and 
these  bodies  may,  therefore,  be  separated  from  the  natural 
combinations  in  which*  they  occur  precisely  as  we  should 
separate  lime,  or  potash,  or  magnesia  in  their  salts. 
Most  of  the  vegetable  alkalies  are  poisonous  bodies,  and, 
indeed,  among  them  we  meet  with  some  of  the  most  ter- 
rific poisons  known.  There  are  several  recently-discov- 
ered artificial  substances,  such  as  Aniline,  and  those  con- 
taining arsenic  and  platinum,  which  ought  to  be  classed 
with  these  basic  bodies. 

What  are  the  vegetable  alkalies  ?  What  element  do  they  aH  contain  ? 
In  what  condition  are  they  commonly  found  ?  What  are  their  relations  to 
acid  bodies?  What  are  their  general  properties?  Have  any  of  them 
been  made  artificially  ? 


368  MORPHIA. NAKCOT1NE. 

Of  the  numerous  vegetable  alkalies,  those  which  I  shall 
now  describe  are  the  most  important. 

Morphia  (C^H^NO^  +  2HO). — This  substance  is  the 
active  principle  of  ppium,  and  was  the  first  discovered  of 
these  alkalies.  It  was  insulated  by  Sertuerner  in  1803. 
It  may  be  prepared  by  mixing  a  concentrated  infusion  of 
opium  with  a  solution  of  chloride  of  calcium  in  excess ; 
the  mixture,  when  warmed,  deposits  a  precipitate  of  me- 
conate  and  sulphate  of  lime,  and  the  hydrochlorate  of  mor- 
phia remains  m  solution.  From  this  it  may  be  crystal- 
lized by  evaporation,  and  a  dark  liquor,  containing  nar- 
cotine  and  coloring  matter,  separated  by  pressure  in  a 
piece  of  flannel.  The  impure  hydrochlorate  may  be  re- 
dissolved  and  re-crystallized,  and,  by  repeating  the  opera- 
tion, or  resorting  to  animal  charcoal,  it  may  be  obtained 
quite  white.  The  salt  may  now  be  dissolved  in  hot  water 
and  acted  on  by  an  excess  of  ammonia,  which  throws 
down  pure  morphia  as  a  white  precipitate.  It  may  be 
obtained  in  crystals  by  solution  in  alcohol. 

Morphia  is  almost  insoluble  in  water;  it  neutralizes 
acids,  and  forms  cry stalliz able  salts.  Its  solution  is  bit- 
ter. It  dissolves  readily  in  dilute  acids,  and  yields  a  deep 
orange-red  color  when  acted  on  by  strong  nitric  acid. 
The  most  common  of  its  salts  are  the  hydrochlorate,  the 
sulphate,  and  the  acetate. 

Narcotine  (C^H^NO15)  is  associated  with  morphia  in 
opium.  It  may  be  obtained  by  digesting  the  insoluble 
portion  with  dilute  acetic  acid  ;  the  precipitate  produced 
by  ammonia  is  to  be  dissolved  in  alcohol,  and  purified  by 
animal  charcoal.  It  yields  prismatic  crystals,  insoluble  in 
water,  and  is  a  weak  base.  By  the  action  of  peroxide  of 
manganese  and  sulphuric  acid,  and  by  bichloride  of  plati- 
num, it  yields  an  extensive  series  of  bodies,  some  of  which 
are  acids  and  others  bases. 

Codeine  (C^HWNO5}. — The  hydrochlorate  of  morphia, 
prepared  as  above  described,  contains  this  base ;  and  when 
the  precipitation  with  ammonia  is  made  it  remains  in  so- 
lution. When  pure,  it  crystallizes  in  octahedrons,  and  is  a 
powerful  base.  Along  with  this  body,  in  opium  there  oc- 
casionally occur  other  substances  of  less  importance,  as 
Tkelaine^  Pseudomorphine,  Narceine,  and  Meconine. 

From  what  is  morphia  obtained  ?  When  was  it  discovered  ?  Give  a 
process  for  its  preparation.  How  is  narcotine  prepared  ?  What  are  its 
properties  ?  What  other  alkaline  bodies  are  obtained  from  opium? 


Q,U1NA. CINCHONA.  369 

Meconic  Acid  (C^HO^,  3HO). — A  tribasic  acid,  asso- 
ciated with  morphia  in  opium.  It  may  be  obtained  from 
the  meconate  of  lime,  which  precipitates  in  the  prepara- 
tion of  morphia  by  mixing  it  with  warm  dilute  hydro- 
chloric acid,  and  repeating  the  operation  until  all  the 
lime  is  removed.  When  purified  from  coloring  matter,  it 
crystallizes  in  scales,  which  are  soluble  in  water  and  al- 
cohol. When  heated,  it  loses  six  atoms  of  water  of  crys- 
tallization ;  and  if  its  solution  be  boiled,  or  the  dry  acid 
heated  in  a  retort,  Comenic  Acid,  CnH2O^  2HO,  a  biba- 
sic  acid  forms  with  the  disengagement  of  water  and  carbon- 
ic acid.  Meconic  acid  yields,  with  the  persalts  of  iron,  a 
blood-red  solution.  It  forms  several  series  of  salts,  like 
all  tribasic  acids. 

Comenic  acid,  when  heated,  yields  carbonic  acid  and  a 
new  body,  Pyromeconic  Acid,  with  a  small  quantity  of  an- 
other substance,  parameconic  acid.  Pyromeconic  acid  is 
composed  of  CloHAOa,  HO. 

Quina — Quinine  (CMH12NO^). — This,  which  is  one  of 
the  most  valuable  of  the  vegetable  alkalies,  is  obtained 
from  Cinchona  Bark.  The  decoction  of  the  ground  bark 
in  dilute  hydrochloric  acid  is  to  be  boiled  in  an  excess  of 
milk  of  lime,  and  the  precipitate  acted  upon  by  boiling 
alcohol ;  on  evaporation  Cinchona  is  deposited  in  crystals, 
but  the  quina  remains  in  solution.  It  may  be  precipitated 
by  the  addition  of  water,  and  obtained  in  crystals  from 
the  spontaneous  evaporation  of  its  solution  in  absolute  al- 
cohol. Quina  neutralizes  acids  perfectly,  giving  rise  to 
salts,  of  which  the  hydrochlorate,  phosphate,  sulphate, 
&c.,  are  employed  in  medicine.  It  is  sparingly  soluble 
in  water,  but  very  soluble  in  alcohol  or  acids.  The  basic 
sulphate  of  quina,  a  common  preparation,  is  sparingly  sol- 
uble in  water,  but  the  neutral  sulphate  is  much  more  so. 
For  this  reason,  sulphate  of  quina  is  often  dissolved  in  di- 
lute sulphuric  acid. 

Cinchona  (C^H^NO). — This  alkali  is  obtained,  as  just 
stated,  in  the  preparation  of  quina,  with  which  it  is  asso- 
ciated in  bark,  and  is  found  in  large  quantity  both  in  the 
gray  and  red  bark.  It  crystallizes  in  prisms,  is  sparing- 
How  is  meconic  acid  procured  ?  "What  is  the  action  of  heat  upon  it  ? 
What  color  does  meconic  acid  yield  with  persalts  of  iron  ?  When  comenio 
acid  is  heated,  what  acids  does  it  yield?  From  what  source  is  quina  de 
rived  ?  How  is  cinchona  prepared  ? 


370 


STRYCHNIA. — 'BRUC1A. 


ly  soluble  in  water.     Its  salts,  like  those  of  the  foregoing, 
are  very  bitter. 

Two  other  analogous  bodies  exist  in  different  species 
of  bark.  They  are  Chinoidine  and  Aricine. 

Kinic  Acid  (C^HnOn,  HO)  is  associated  with  the  fore- 
going bodies  in  bark.  It  is  obtained  by  decomposing  the 
kinate  of  lime,  obtained  in  the  manufacture  of  sulphate  of 
quina  by  oxalic  acid,  filtering  the  solution  from  oxalate 
of  lime,  and  the  kinic  acid  crystallizes  on  evaporation.  It 
is  very  soluble  in  water. 

Strychnia  ( C^H^N^  O4)  occurs  in  Nux  Vomica,  St.  Ig- 
natius's  Bean,  in  the  poison  Upas  Tieute,  and  other  vege- 
table products.  It  may  be  extracted  from  nux  vomica 
seeds  by  boiling  them  in  dilute  sulphuric  acid,  and  then 
acting  with  lime  and  alcohol  as  described  in  the  case  of" 
quina. 

Strychnia  requires  7000  parts  of  water  for  solution,  and 
communicates  to  it  an  intensely  bitter  taste.  It  is  one  of 
the  most  violent  poisons  known.  Its  alkaline  powers  are 
well  defined,  and  it  produces  a  complete  series  of  salts. 
It  is  soluble  in  hot  alcohol,  but  not  in  ether.  The  anti- 
dote for  an  over-dose  of  it  is  an  infusion  of  tea. 

Brucia  (C^Hi5N,2O7)  is  associated  with  strychnia, -and, 
being  very  soluble  in  cold  alcohol,  is  readily  separated 
from  it.  It  is  also  more  soluble  in  hot  water,  and  pos- 
sesses the  poisonous  character  of  strychnia.  These  sub- 
stances are  found  in  union  with  Igasuric  Acid. 

The  following  table  gives  the  names  of  other  vegetable 
alkalies,  and  bodies  analogous  to  them  : 


Aconitine. 

Daturine. 

Picrotoxine. 

Antearine. 

Delphinine. 

Pipeline. 

Asparagine. 

Elaterine. 

Phloridzine. 

Atropine. 

Emetine. 

Popnliuev 

C  affeine  —  Theine. 

Gentianine. 

Salicine. 

Chelidonine. 

Hesperidine. 

Solaniae. 

Chinoidine. 

Hyosciamine. 

Stramonine. 

Colchicine. 

Meconine. 

Thebaine. 

Conine. 

Narceine. 

Theobromine. 

Curarine. 

Narcotine. 

Veratrine. 

Daphnine. 

Of  some  of  these  bodies,  as  nicotine  and  conine,  it  may 

What  other  alkalies  exist  in  bark  ?  With  what  acids  are  these  bodies 
associated  ?  From  what  sources  is  strychnia  procured  ?  What  are  the 
properties  of  strychnia?  What  is  the  best  antidote  to  its  poisonous  ef- 
fects? With  what  other  alkali  is  it  associated?  Mention  some  othei 
vegetable  alkalies. 


COLORING    BODIES.  371 

oe  remarked  that  they  are  volatile  oily  liquids,  which  can 
form  crystallizable  salts  and  acids.  They  both  contain 
nitrogen,  and  are  interesting  in  their  relations  to  the  three 
following  bodies,  which  may  be  formed  artificially. 

Aniline  ( C^HjN). — This  substance  is  formed  by  the  ac- 
tion of  potash  on  isatine,  and  is  also  one  of  the  ingredi- 
ents of  the  oil  of  coal  tar.  It  is  an  oily  liquid,  boils  at 
358°,  and  yields  crystalline  salts  with  acids. 

Leukol  (CiSHsN). — Formed  with  the  foregoing  in  oil  of 
coal  tar,  from  which  it  may  be  separated  by  distillation. 
it  is  also  an  oily  liquid,  and  can  yield  crystallizable  salts. 

Quinoline  ( C19HSN). — Formed  by  distilling  quinine  or 
strychnine  with  caustic  potash.  An  oily  liquid,  very  bit- 
ter, strongly  alkaline,  and  yielding  crystallizable  salts. 

Besides  these  bodies  there  are  other  artificial  bases  of 
an  analogous  nature,  but  which  differ  in  the  remarkable 
particular  of  containing  platinum  and  arsenic ;  such,  for 
example,  as  the  platina  bases  of  Reiset  and  Gros,  or  the 
arsenico-platinum  radical  kakoplatyle.  The  formation  of 
these  organic  bases  leads  us  to  hope  that  the  vegetable 
alkalies  themselves  will  hereafter  be  artificially  formed. 


LECTURE  LXXXIH. 

THE  COLORING  BODIES.  —  General  Properties  of  Color- 
ing Principles.  —  Madder.  —  Hcematoxyline. —  Gartha- 
mine.  —  Yellow  Colors.  —  Chlorophyll.  —  Indigo. — Sul- 
phindigotic  Acid.  —  Deoxydized  Indigo.  —  Action  of 
Heat  and  Reagents  on  Indigo. — Litmus. —  Carmine. 

THE  coloring  principles  derived  from  the  organic  king- 
dom may  be  conveniently  divided  into  two  classes :  the 
non-nitrogeriized  and  the  nitrogenized.  They  may  also 
be  readily  classed  into  groups,  as  blue,  red,  yellow,  green. 
For  the  most  part  they  are  derived  from  vegetable  pro- 
ductions. 

For  some  coloring  matters  the  fibres  of  those  tissues 
commonly  employed  for  clothing  have  a  sufficient  affinity 
as  to  hold  the  color  so  that  it  can  not  be  removed  by  mere 

What  analogous  substances  have  been  formed  artificially  ?  What  may 
be  remarked  as  respects  the  salts  of  Reiset  and  Gros  ?  How  may  color- 
ing principles  be  classified  ? 


372  NON-NITROGENIZED    COLORS, 

washing,  and  is  permanently  dyed.  But  in  other  in- 
stances this  is  not  the  case  ;  the  artist  then  has  to  avail 
himself  of  the  qualities  possessed  by  intermediate  bodies, 
such  as  alumina  and  the  oxide  of  tin,  which  at  once  pos- 
sess the  double  quality  of  an  affinity  for  the  coloring  mat- 
ter and  an  affinity  for  the  cloth  fibre.  The  attraction  of 
these  bodies  for  coloring  matter  may  be  illustrated  by 
precipitating  alumina  in  a  solution  tinged  by  litmus ;  the 
solution  becomes  perfectly  clear,  its  color  going  down 
with  the  precipitate,  and  forming  with  it  a  lake. 

NON-NITROGENIZED  COLORING  MATTERS. 

The  Blue  non-nitrogenized  coloring  matters  are  chiefly 
found  in  flowers  and  fruits.  They  are  reddened  by  acids, 
and  turned  green  by  alkalies. 

The  Red  non-nitrogenizing  coloring  matters  are  of 
some  importance ;  among  them  may  be  mentioned  Mad- 
der Red,  the  sublimed  crystals  of  which  are  known  as  Ali- 
zarine (C37Hl2Oio).  Madder  also  furnishes  a  purple  and 
a  yellow  color. 

H<zmatoxyline  ( C40HnO15)  is  the  coloring  matter  of  log- 
wood ;  it  is  soluble  in  water  and  alcohol,  and  furnishes, 
with  iron  salts,  the  black  dye  for  hats.  The  same  princi- 
ple is  yielded  by  Brazil-wood  and  cam-wood.  Cartha- 
*nine  is  a  very  beautiful  red,  obtained  from  safflower;  it 
*j  used  for  making  pink  saucers. 

The  Yellow  coloring  matters.  Among  these  may  be 
mentioned  Quercitrine  (Cl6HKOg,  HO),  derived  from  the 
Quercus  Tinctoria  ;  Gamboge,  the  dried  juice  of  the  Gar- 
cinia  Gambogia  ;  Turmeric,  used  as  a  test  for  alkalies, 
which  turn  it  brown,  from  the  Curcuma  Longa ;  and 
Anatto,  from  the  seeds  of  the  Bixa  Orellana. 

The  Green  coloring  matters.  Chlorophyll,  the  constitu- 
tion of  which  is  not  known.  It  is  the  green  coloring  mat- 
ter of  leaves.  It  is  insoluble  in  water,  but  soluble  in  al- 
cohol and  ether,  and  is  a  fatty  substance.  It  is  also  found, 
under  very  interesting  circumstances,  in  the  animal  sys- 
tem as  the  coloring  matter  of  bile. 


From  what  source  are  the  blue  non-nitrogenized  colors  obtained  ?  What 
is  alizarine  ?  "What  are  haematoxyline  and  carthamine  ?  From  what 
sources  are  quercitrine,  gamboge,  turmeric,  and  anatto  derived  1  What  is 
chlorophyll  1 


1JND1GO.  373 

NITROGENIZED  COLORING  MATTERS. 

The  nitrogenized  coloring  matters,  among  which  are 
some  of  the  most  valuable  dyes  that  we  possess,  may  also 
be  divided  according  to  their  tint. 

Indigo  is  derived  from  the  juice  of  several  species  of 
Indigofera,  and  is  formed  from  a  colorless  or  yellow  com- 
pound which  is  dissolved  out  from  the  leaves  of  these 
plants  when  they  are  allowed  to  ferment  with  water.  A 
ideep  blue  precipitate  (indigo)  forms.  It  appears,  there- 
fore, to  be  a  product  of  oxydation.  It  comes  in  com- 
merce in  small  masses,  which,  when  rubbed,  exhibit  a 
coppery  aspect,  is  insoluble  in  water,  alcohol,  dilute 
acids,  and  alkalies,  and  may  be  sublimed,  yielding  a  pur- 
ple vapor,  which  condenses  into  crystals  of  pure  indigo. 
It  dissolves  in  about  fifteen  parts  of  strong  sulphuric  acid, 
but  still  better  in  Nordhausen  oil  of  vitriol,  yielding  a 
mass  which  is  soluble  in  water.  It  is  Sulphindigotic  Acid. 
By  contact  with  deoxydizing  agents,  blue,  indigo  becomes 
colorless,  as  may  be  shown  by  digesting  powdered  indigo, 
green  vitriol,  hydrate  of  lime,  and  water  together.  In 
this  state,  as  in  its  natural  condition,  it  is  soluble  in  wa- 
ter, and  white  indigo  may  be  precipitated  by  hydrochloric 
acid.  On  exposure  to  the  air,  deoxydized  indigo  absorbs 
oxygen  rapidly,  and  becomes  blue  and  insoluble. 

When  indigo  is  submitted  to  destructive  distillation  it 
yields  an  oily  liquid,  Aniline,  possessed  of  powerfully 
basic  properties,  and  described  in  the  last  Lecture. 

The  relation  which  exists  between  blue  and  white  indi 
go  is  seen  from  their  formulas. 

Blue  indigo C^H^NO^. 

White  indigo CieHsNOi. 

By  several  chemists  indigo  is  regarded  as  containing  a 
radical,  Anyle,  =  C16H5N,  the  symbol  for  which  is  An. 
On  this  view,  blue  indigo  is  the  anhydrous  deutoxide  of 
anyle,  AnO^  and  white  indigo  the  hydrated  protoxide, 
AnO,  HO. 

Under  the  action  of  heat  and  of  reagents,  indigo  yields 
an  extensive  class  of  bodies,  to  which  much  attention  has 
been  given.  In  this  place  I  can  do  little  more  than  enu- 
merate some  of  them.  With  dilute  nitric  acid  it  yields 

From  what  source  is  indigo  derived  ?  How  is  sulphindigotic  acid  made  ? 
What  is  deoxydized  indigo  ?  How  is  aniline  made  ?  What  is  the  rela- 
tion between  blue  and  white  indigo  ?  What  is  anyle  ? 

I  I 


374  LITMUS. CARMINE. 

Anilic  or  Indigotic  Acid.  With  strong  nitric  acid  it  yields 
Picric  or  Carbazotic  Acid,  a  substance  of  a  yellow  color, 
bitter  taste,  and  forming  explosive  salts.  Heated  with 
bichromate  of  potash,  sulphuric  acid,  and  water,  it  yields 
Isatine,  which  crystallizes  in  red  prismatic  crystals,  and 
contains  the  elements  of  blue  indigo,  with  two  additional 
atoms  of  oxygen.  This  body,  under  the  influence  of  an 
alkaline  solution,  unites  with  one  atom  of  water,  and 
changes  into  Isatinic  Acid.  Under  the  influence  of  chlo- 
rine, isatine  yields  Chlorisatine,  by  an  atom  of  chlorine 
substituting  one  of  its  hydrogen  atoms,  and  Bichlorisatine, 
by  the  substitution  of  two  chlorine  atoms  for  two  hydro- 
gen ones ;  and  these,  again,  as  in  the  case  of  isatine  itself, 
acted  upon  by  alkaline  solutions,  yield  each  an  acid. 
Caustic  alkalies,  acting  on  indigo,  yield  Crysanilic  and 
Anthranilic  Acids. 

Litmus  is  derived  from  the  RocclJa  Tinctoria,  Lccanora 
Tartarea,  &c.  These  lichens  yield  to  ether  a  crystalline 
substance,  to  which  the  name  Lecanorine  is  given.  It 
does  not  contain  nitrogen.  It  is  in  white  crystals,  soluble 
in  hot  alcohol  and  ether.  This  substance,  heated  with 
baryta  or  alkalies,  yields  Orcine,  by  losing  two  atoms  of 
carbonic  acid.  Orcine  crystallizes  in  prisms,  which  have 
a  yellowish  tint  and  a  sweet  taste.  Mixed  with  ammonia, 
and  exposed  to  the  air,  oxygen  is  absorbed,  and  the  liquid 
assumes  a  deep  purple  tint.  From  this  acetic  acid  precip- 
itates a  deep-red  powder,  Orceine,  C16H9NO7,  which  con- 
tains nitrogen,  and  is  supposed  to  be  the  basis  of  the  dye 
stuff  of  litmus.  With  alkalies  it  gives  a  blue  color.  Lit- 
mus is  extensively  used  in  chemistry  as  a  test  for  acids 
and  alkalies. 

Carmine  is  the  coloring  matter  of  the  cochineal  insect, 
Coccus  Cacti.  The  coloring  matter  may  be  obtained  from 
the  insect  by  water  or  ammonia.  The  carmine  of  com- 
merce is  a  lake  containing  alumina. 

Aloes  is  the  inspissated  juice  of  certain  species  of  Aloe, 
used  as  a  purgative  medicine.  When  heated  with  nitric 
acid,  and  water  added,  a  yellow  precipitate  is  thrown 
down,  which,  when  purified,  is  Chrysammic  Acid.  It 

What  are  indigotic  acid,  carbazotic  acid,  and  isatine  ?  What  is  the  effect 
of  alkaline  solutions  on  isatine  ?  What  is  the  effect  of  chlorine  upon  it  ? 
From  what  sources  is  litmus  derived  ?  What  are  orcine  and  orceuie  ? 
From  what  source  is  carmine  derived?  How  is  chrysammic  acid  pre- 
pared? 


THE    FATTY    BODIES.  375 

yields  yellow  crystals  of  a  bitter  taste,  and  furnishes  a 
solution  of  a  purple  color.  Its  salts  are  crystallizable,  by 
transmitted  light  of  a  red  color,  with  a  green  metallic  re- 
flection like  murexide.  The  liquid  from  which  this  acid 
was  precipitated  contains  picric  acid. 


LECTURE  LXXXIV. 

THE  FATTY  BODIES. — Properties  of  the  Saponifiable  Fats. 
— Distinction  between  Fixed  and  Volatile  Oils. — Prep- 
aration of  Soaps. — Stearine  and  Stearic  Acid. — Mar- 
garine and  Margaric  Acid. — Oleine  and  Oleic  Acid. — 
Margarone. — Production  of  Glycerine. — Natural  Oils, 
as  Palm  Oil,  Cocoa  Talloiv,  and  Nutmeg  Butter. — 
Spermaceti. — Cholesterine. —  Three  Classes  of  Volatile 
Oils. —  The  Camphors. 

THIS  class  of  substances  is  characterized  by  several 
well-marked  peculiarities,  and  may  be  conveniently  di- 
vided into  two  natural  groups,  oils  and  fats.  They  belong 
both  to  the  vegetable  and  animal  systems.  In  the  former 
they  usually  abound  in  the  seeds  or  fruits ;  in  the  latter 
they  are  deposited  in  the  cellular  structure  of  the  adipose 
tissue.  The  natural  fats  are  usually  mixtures  of  two  or 
more  ingredients,  which  differ  from  one  another  in  con- 
sistency. In  most  instances  they  are  stearine  and  mar- 
garine, along  with  a  liquid  oleine.  These  oils  can  not  be 
distilled  without  undergoing  decomposition  ;  exposed  to 
the  air,  they  gradually  absorb  oxygen  and  evolve  carbonic 
acid.  Many  of  them,  in  which  this  change  takes  place 
with  rapidity,  turn  into  resinous  bodies  ;  and  hence  their 
application,  in  the  art  of  painting,  as  drying  oils.  When 
acted  upon  by  alkalies,  the  fixed  oils  and  fats  give  rise  to 
soaps,  and  hence  are  spoken  of  as  Saponifiable. 

Oily  bodies  may  be  divided  into  fixed  and  volatile. 
The  fixed  oils  decompose  when  heated ;  the  volatile  ones 
distill.  A  simple  test,  therefore,  is  sufficient  to  distinguish 
them.  When  a  few  drops  of  an  oily  substance  are  put  on 
paper,  if  it  be  a  volatile  oil  it  goon  evaporates,  and  leaves 

Into  what  natural  groups  may  the  fatty  bodies  be  divided  ?  "What  are 
the  natural  fats  ?  What  change  do  the  drying  oils  undergo  ?  How  may 
the  fixed  oils  be  distinguished  from  the  volatile  ? 


376  SAPONIF1CAT1ON. 

the  paper  without  a  stain ;  if  fixed,  the  paper  remains 
greasy.  The  fixed  oils  have  but  little  odor,  the  volatile 
oils  commonly  a  characteristic  one.  They  are  all  insol- 
uble in  water ;  many  of  them  are  soluble  in  alcohol ;  but 
in  ether  they  are  freely  dissolved. 

By  exposure  to  a  low  temperature  the  constituent  prin- 
ciples of  a  mixed  oil  may  often  be  separated  from  each 
other,  the  more  solid  substances  separating  as  the  tem- 
perature .descends.  When  olive  oil  is  thus  treated,  an 
exposure  of  40°  F.  causes  a  deposit  of  Margarine :  the 
fluid  portion  which  is  left  is  Oleine.  Animal  fats  exposed 
to  pressure  between  folds  of  blotting  paper  communicate 
to  it  oleine,  and  the  solid  residue  which  is  left  behind  is  a 
mixture  of  margarine  and  Stearine.  When  the  fixed  fats 
are  boiled  with  alkaline  solutions,  Soaps  are  formed ; 
these  substances,  which  are  of  extensive  use  in  domestic 
economy  and  the  arts  from  their  detergent  qualities,  are 
freely  soluble  in  water.  In  the  process  of  making  them, 
the  fats  undergo  a  change  ;  they  form  true  acids,  stearine 
yielding  stearic  acid,  margarine  margaric  acid,  and  oleine 
oleic  acid,  which  may  be  set  free  by  decomposing  the 
soap  with  an  acid.  With  them  there  is  also  formed  a 
sweet  substance,  Glycerine,  which  appears  to  be  the  same, 
whatever  fat  may  have  been  originally  employed.  Of 
the  varieties  of  soap  met  with  in  commerce,  Soft  Soap  is 
made  from  potash,  combined  with  whale  or  seal  oil;  Hard 
White  Soap  from  tallow  and  caustic  soda ;  Hard  Yellow 
Soap  from  soda,  tallow,  palm  oil,  and  resin.  In  the  prep- 
aration of  white  soap  the  alkaline  solution  is  made  to  boil, 
and  tallow  added  in  small  portions  until  no  more  can  be 
saponified ;  the  solution  now  contains  soap  and  free  gly- 
cerine ;  the  former  is  separated  by  the  addition  of  com- 
mon salt,  in  a  solution  of  which  it  is  insoluble.  It  floats 
011  the  top  of  the  liquid.  It  is  then  run  into  moulds,  and 
cut  into  bars  for  commerce.  In  this  process  the  manu- 
facturer does  not  add  so  much  salt  as  to  separate  all  the 
water.  Commercial  soap  still  contains  from  40  to  50  per 
cent. 

Stearine  may  be  obtained  from  purified  mutton  fat  by 

What  is  the  difference  of  their  properties  ?  What  is  the  effect  of  a  re- 
duction" of  temperature  on  mixed  oils?  Into  what  may  olive  oil  be  thus 
decomposed  ?  What  are  soaps  ?  How  may  the  different  varieties  be 
formed  ?  How  is  stearine  prepared,  and  what  are  its  properties  ? 


STEARIC    AND    MARGARIC    ACIDS.  377 

suffering  a  warm  ethereal  solution  to  cool.  The  stearine 
crystallizes,  and  margarine  arid  oleine  are  left  in  solution. 
A  repetition  of  the  process  purifies  it.  It  is  a  white  body, 
insoluble  in  water  and  in  cold  alcohol.  It  melts  at  130°. 
When  saponified,  it  yields  glycerine  and  stearic  acid. 

Stearic  Acid  (C^H^O-^  may  be  crystallized  from  a  hot 
alcoholic  solution,  is  insoluble  in  water,  and  without  taste 
or  smell.  It  is  soluble  both  in  alcohol  and  ether,  melts 
at  158°,  and  may  be  volatilized  without  change. 

Margarine. — This  substance  remains  with  oleine  in  the 
ethereal  solution  arising  in  the  preparation  of  stearine, 
and  may  be  obtained  from  it  by  evaporation  and  pressing 
the  soft  mass  in  paper.  Margarine  is  found  more  abund- 
antly in  human  than  in  other  kinds  of  fat. 

Margaric  Acid  (C6SH^O6)  is  prepared  by  saponifying 
margarine  with  potash  and  decomposing  with  hydrochlo- 
ric acid.  It  is  also  formed  with  other  products  by  the 
distillation  of  stearic  acid.  It  crystallizes  in  white  nee- 
dles, its  melting  point  being  140°. 

Oleine. — When  almond  or  rape  oil  is  dissolved  in  ether 
and  the  solution  exposed  to  a  low  temperature*the  mar- 
garine crystallizes,  and  oleine  may  be  obtained  by  evap- 
orating the  ether.  It  remains  liquid  at  a  temperature  of 
0°.  From  it  Oleic  Acid  (C^H^O.,)  may  be  obtained  by 
saponification  and  decomposition  with  muriatic  acid,  as  in 
the  foregoing  instances.  Its  melting  point  is  about  20°. 
It  gives  rise  to  a  class  of  salts. 

Margarone  (C^H^O^. — When  a  mixture  of  margaric 
acid  and  lime  ^s  distilled  this  substance  is  formed,  and 
carbonic  acid  separates.  It  is  a  white  solid,  like  sperma- 
ceti, and  melts  at  170°. 

Glycerine  (CCH8O6). — This  substance  arises  when  any 
fatty  matter  is  saponified  with  potash,  the  soap  being  de- 
composed with  tartaric  acid,  and  dissolving  the  glycerine 
out  by  alcohol.  It  is  a  colorless  liquid,  specific  gravity 
1-26  ;  it  is  soluble  in  water  and  alcohol,  but  not  in  ether. 
It  may  be  cooled  to  a  very  low  point  without  assuming 
the  solid  form.  When  mixed  with  sulphuric  acid,  the 
two  bodies  unite  directly,  and  Sulplioglyceric  Acid  is 

What  is  th<?  process  for  preparing  stearic  acid?  How  are  margarine 
and  margaric  acid  obtained  ?  What  are  the  properties  of  oleine  ?  How 
is  oleic  acid  made  ?  What  is  margarone  ?  Under  what  circumstances 
does  glycerine  form  ? 

I  i  2 


378  FATTY    BODIES. 

I 

the  result:    an   acid   having   many  analogies    with   sul- 
phovinic. 

Palm  Oil  is  brought  from  Africa,  and  much  of  it  used 
in  the  manufacture  of  yellow  soap.  It  is  of  a  reddish- 
yellow  color,  and  contains,  besides  oleine,  a  solid  fat,  Pal- 
mitine.  It  is  insoluble  in  water,  slightly  soluble  in  hot  al- 
cohol, but  very  soluble  in  ether.  Its  melting  point  is  118°. 
By  saponifieation  and  decomposition  with  an  acid,  it  yields 
Palmitic  Acid,  the  melting  point  of  which  is  140°.  It  is 
a  bibasic  acid. 

Cocoa  Tallow. — A  solid  fat  obtained  from  the  cocoa- 
nut,  and  used  in  the  manufacture  of  candles.  Its  oleine 
and  stearine  may  be  separated  by  pressure,  or  by  boiling 
alcohol,  from  which  the  stearine  crystallizes  on  cooling. 

Among  other  fatty  substances  and  allied  bodies  may 
be  mentioned  Nutmeg  Butter,  which  yields,  among  other 
products,  Myristicine,  and  by  saponification,  Myristic  Acid. 
Elaidine,  which  arises  from  the  action  of  nitrous  acid  on 
oleine  ;  it  furnishes,  by  the  common  process,  Elaidic 
Acid.  Suberic  Acid,  which  arises  from  the  action  of  nitric 
acid  on  cork.  Succinic  Acid,  by  the  destructive  distilla- 
tion of  amber,  or  by  the  continued  action  of  nitric  on 
stearic  acid.  Sebacic  Acid,  by  the  destructive  distilla- 
tion of  oleic  acid.  Butyrine,  Caproine,  and  Caprine^ 
which  are  contained  in  butter.  These  yield,  by  saponifi- 
cation and  decomposition,  Butyric,  Caproic,  and  Capric 
Acids.  Butyric  acid  can  be  made,  as  we  have  seen,  ar- 
tificially by  fermentation.  Bves'  Wax  is  a  mixture  of  two 
bodies  :  Cerine,  which  may  be  dissolved  by  boiling  alco- 
hol, and  Myricine,  which  is  insoluble  therein.  Spermaceti, 
which  is  obtained  from  certain  species  of  whales,  yields, 
under  the  process  for  glycerine,  a  substance,  Etkal,  and 
this,  under  the  action  of  hot  potash,  gives  Ethalic  Acid, 
With  evolution  of  hydrogen  gas.  Cholesterine  is  obtained 
from  biliary  calculi ;  it  also  occurs  in  the  substance  of  the 
brain. 

THE  VOLATILE  OILS. — These,  for  the  most  part,  are 
found  in  plants,  or  are  derived  from  them  by  simple  proc- 
esses. Many  of  them  are  extensively  used  in  the  arts  in  the 

What  are  palm  oil,  palmitine,  and  palmitic  acid  ?  Mention  some  other 
bodies  belonging  to  the  same  class.  From  what  are  suberic,  succinic,  and 
sebacic  acids  derived  ?  What  bodies  are  contained  in  butter,  and  what 
acids  do  they  yield?  What  two  substances  are  found  in  bees'  wax? 
From  what  are  spermaceti  and  cholesterine  derived  7 


VOLATILE    OILS.  379 

manufacture  of  varnishes,  and  others  in  the  preparation 
of  perfumery.  Their  solutions  in  alcohol  form  Essences, 
and  in  water  Medicated  Waters.  They  are  commonly 
obtained  by  the  distillation  of  those  parts  of  the  plants  in 
which  they  occur,  with  water,  and  consist  of  two  substan- 
ces, a  solid  portion,  Stearopten,  or  camphor,  and  a  true  oil. 
They  may  be  divided  into  groups  according  to  their  con- 
stitution. 

Volatile  Oils  containing'  Carbon  and  Hydrogen. 


Turpentine. 

Citron. 

-Copaiva. 


Bergamotte. 
Cubebs, 
&c. 


Storax. 

Volatile  Oils  containing'  Carbon,  Hydrogen,  and  Oxygen. 
Cajeput.  Pennyroyal. 

Lavender.  Valerian. 

Rosemary.  Spearmint, 

Peppermint.  &c. 

Volatile  Oils  containing  Sulphur. 
Black  mustard.  Onions. 

Horseradish.  Asafoetida. 

The  stearoptens  (camphors)  of  the  volatile  oils  are  best 
represented  by  common  camphor,  which  is  extracted  from 
the  Laurus  and  Dryabalonops  Campkora  by  distilling  with 
water.  It  is  a  white,  tough,  semitransparerit  mass,  light- 
er than  water,  of  a  well-marked  odor,  melts  at  350°,  and 
soon  after  sublimes  rapidly  unchanged.  Artificial  Cam- 
phor is  made  by  passing  dry  muriatic  acid  gas  into  oil  of 
turpentine.  It  is  a  muriate  of  oil  of  turpentine.  The 
true  camphors  originate  in  several  different  ways  ;  some- 
times by  the  oxydation  of  the  oils  from  which  they  are 
derived ;  sometimes  they  are  hydrates  of  those  oils ;  and 
sometimes  they  are  isomeric  with  them. 

Into  what  groups  may  the  volatile  oils  be  divided  ?    What  are  the  cam- 
phors 1     What  is  common  and  artificial  mirmiim.? 


380  RESINS. BALSAMS. 


LECTURE  LXXXV. 

THE  RESINS,  BALSAMS,  AND  BODIES  ARISING  IN  DESTRUC- 
TIVE DISTILLATION. — Colophony,  Gum  Lac,  Amber,  fyc. 
— India-rubber. — BAL  SAMS. — Products  of  the  Destructive 
Distillation  of  Wood. — Parajfine,  Eupione,  Creasote,  and 
allied  Bodies. —  The  Destructive  Distillation  of  Coal. — 
Naphthaline,  Paranaphthaline,  Kyanol,  Carbolic  Acid. 
— Products  of  slow  Decay. —  Ulmine  and  Ulmic  Acid. — 
Crenic  and  Apocrenic  Acid. —  The  Varieties  of  Coal  and 
other  subsidiary  Bodies. 

THE  resins  are  bodies  in  many  respects  analogous  to 
the  camphors,  but  are  distinguished  from  them  by  the  cir- 
cumstance that  they  are  not  volatile  without  decomposi- 
tion". In  many  instances  they  act  as  acids ;  they  all  con- 
tain oxygen. 

Colophony  is  a  mixed  resin,  obtained  by  the  distillation 
of  turpentine  with  water,  the  oil  of  turpentine  passing  over. 
It  is  a  mixture  of  two  resins,  Pinic  and  Sylvic  Acids,  which 
may  be  separated  by  cold  alcohol,  in  which  sylvic  acid  is 
insoluble. 

Gum  Lac,  which  is  one  of  the  resins,  occurs  under  three 
forms  :  shell  lac,  stick  lac,  and  seed  lac.  It  is  used  in  the 
preparation  of  lacquers,  and  is  the  chief  ingredient  in  seal- 
ing-wax. Among  other  resins  may  be  mentioned  Copal\ 
Mastic,  Dragon's  Blood,  Gamboge,  Sandarac,  and  Dam- 
mara  Resin. 

Amber  is  a  substance  belonging  to  this  class.  It  is  form- 
ed in  beds  of  bituminous  wood,  and  often  incloses  insects 
x&  a  state  of  beautiful  preservation.  Its  specific  gravity 
is  about  1/07:*  By  distillation  it  yields  succinic  acid. 

Caoutchouc  —  Indian-rubber ,  or  Gum-elastic  —  is  the 
product  of  the  Jatropa  Elastica,  the  Hcevea  Caoutchouc,  and 
several  other  tropical  trees.  The  milky  juice  which  they 
yield  is  dried  on  moulds  of  various  forms ;  it  turns  of  a 
black  color  by  being  smoked.  From  its  imperviousness 

What  are  the  resins  ?  What  substances  may  be  obtained  from  coloph- 
ony ?  What  is  gtun  lac?  What, acid  does  amber  yield  by  distillation? 
From  what  sources  is  India-rubber  derived  ?  What  is  the  cause  of  its 
black  color  ? 


DESTRUCTIVE    DISTILLATION.  381 

to  water,  this  substance  has  of  late  been  introduced  for  a 
great  variety  of  purposes.  It  is  combustible,  burns  with 
a  bright  flame,  is  softened  by  boiling  water,  and  still  more 
so  by  ether.  In  ether,  as  also  in  naphtha  and  coal  oil,  it 
may  be  dissolved.  Bags  of  it,  soaked  in  ether  until  they 
become  gelatinous,  may  be  distended,  by  blowing  into 
them,  to  a  very  great  size,  and  thus  become  useful  for  a 
variety  of  purposes.  Veiy  few  chemical  agents  act  upon 
India-rubber :  it  is  extensively  used  for  connecting  the 
parts  of  chemical  apparatus. 

BALSAMS  are  compounds  of  resins  with  volatile  oils ; 
some  of  them  also  contain  benzoic  or  cinnamic  acids. 
Some,  as  benzoin,  are  solid ;  and  others,  as  the  Balsams 
of  Tolu  and  Peru,  are  viscid  fluids. 

THE  PRODUCTS  OF  THE  DESTRUCTIVE  DISTILLATION  OF 
WOOD,  &e. 

When  wood  is  submitted  to  distillation  in  close  vessels, 
a  black,  inflammable  liquid  called  Tar  is  formed  ;  it  con- 
tains a  great  many  remarkable  bodies,  among  which  the 
following  may  be  mentioned.  The  solid  black  residue 
which  is  left  after  the  distillation  or  inspissation  of  tar 
constitutes  Pitch. 

Paraffine  (C .  H)  is  obtained  by  distilling  tar,  several 
oils  coming  over  :  it  is  from  the*heaviest  that  this  substance 
is  extracted.  It  is  a  solid  substance,  lighter  than  water, 
of  a  fatty  appearance;  it  melts  at  111°  F.,  and  distills 
unchanged.  Few  chemical  agents  act  Upon  it :  it  remains 
unchanged  by  the  alkalies,  acids,  &c.,  but  is  soluble  in 
turpentine  and  naphtha.  From  its  chemical  indifference 
it  has  obtained  its  name  (Parum  Affinis). 

Eupione  (C5-H"6)  occurs  abundantly  in  animal  tar,  from 
which  it  may  be  prepared  by  distillation,  and  subsequent- 
ly purified  by  rectification  from  sulphuric  acid.  From 
paraffine  it  may  be  separated  by  exposure  to  cold,  or, 
being  more  volatile,  by  distillation.  It  is  a  colorless  li- 
quid, specific  gravity  .074;  it  boils  at  339°  F.  It  is  in- 
soluble in  water,  but  very  soluble  in  alcohol. 

Creasote  is  extracted  from  the  heavy  oil  of  tar  by  a 
complicated  process.  It  is  an  oily,  colorless  liquid,  of  a 
burning  taste,  exhaling  a  powerful  odor  of  wood  smoke. 

How  may  it  be  softened,  and  in  what  dissolved?  What  are  the  bal- 
sams ?  What  are  tar  and  pitch  ?  What  properties  distinguish  paraffine  ? 
What  are  the  properties  of  eupione  ? 


382  NAPHTHALINE. 

It  is  slightly  heavier  than  water,  boils  at  400°  F.,  is  com- 
bustible. One  hundred  parts  of  water  dissolve  about  1£ 
of  this  substance,  and  obtain  its  peculiar  odor.  It  has  the 
remarkable  property  of  coagulating  albumen  and  preserv- 
ing flesh  from  putrefactive  changes.  From  this  latter  cir- 
cumstance its  name  is  derived. 

Among  allied  substances  may  be  mentioned  Picamar, 
an  oily  liquid  of  a  bitter  taste,  which  boils  at  518°  F.,  and 
combines  with  bases  to  form  crystalline  compounds.  Kap~ 
nomar,  a  colorless  liquid,  having  an  odor  of  rum ;  boils  at 
360°  F.,  and  forms,  with  oil  of  vitriol,  a  purple  solution. 
Cedriret,  which  forms  red  crystals,  giving,  with  creasote, 
a- purple  solution,  and  with  sulphuric  acid  a  blue.  Pitta- 
kal,  a  dark  blue  solid,  which  yields  blue  precipitates  with 
metallic  salts.  It  contains  nitrogen. 

When  coal  tar  is  submitted  to  distillation,  like  wood 
tar,  it  yields  a  volatile  oil,  which,  by  being  submitted  to 
rectification,  becomes  Coal  Oil,  or  Artificial  Naphtha. 
From  it  a  variety  of  substances  may  be  extracted  ;  they 
either  pre-exist  in  the  oil,  or  are  formed  by  the  operation. 

NAPHTHALINE  (C10H4)  is  obtained  by  rectifying  coal 
gas  tar;  it  forms  colorless  crystalline  plates,  melting  at 
13€°  F.  and  boiling  at  413°  F.  It  exhales  a  peculiar 
odor,  is  very  combustible,*insoluble  in  water,  but  soluble 
in  ether  and  alcohol ;  the  specific  gravity  of  its  vapor  is 
4'52$.  It  dissolves  in  sulphuric  acid,  and  the  solution,  on 
being  diluted  with  water  and  saturated  with  carbonate  of 
baryta,  yields  two  salts,  one  containing  Sulphonaphthalic 
Acid)  and  the  other  an  acid  less  known. 

Paranaphthaline  ( CibHb)  is  associated  with  naphthaline, 
but  differs  from  it  by  being  insoluble  in  alcohol,  by  which 
liquid  they  may,  therefore,  be  separated. 

Kyanol  (Ci2H7N),  an  oily  liquid,  which,  though  volatile, 
has  a  boiling  point  of  358°  F.  It  is  heavier  than  water, 
with  which  it  may  be  combined,  and  is  soluble  in  alcohol 
and  ether.  It  possesses  basic  properties,  and  yields  sev- 
eral well-defined  salts. 

Carbolic  Acid — Hydrate  ofPhenyle  ( &12H-0O) — is  found 
in  that  portion  of  oil  of  tar  which  boils  between  300°  F. 

What  remarkable  properties  does  creasote  possess  ?  From  what  is  its 
name  derived  ?  From  what  sources  are  picamar,  kapnomar,  cedriret,  and 
pittakal  obtained  ?  What  are  the  properties  of  naphthaline  ?  What  sub- 
stance closely  resembles  it?  What  are  the  properties  of  kyanol? 


BODIES  PRODUCED  ,BY  DECAY.          383 

and  400°  F.  This  being  agitated  with  potash,  and  the  re- 
sult decomposed  by  an  acid,  yields  carbolic  acid,  which 
may  be  purified  by  rectification  from  caustic  potash.  It 
is  an  oily  liquid,  but  may  be  obtained  in  long,  needle- 
shaped  crystals.  A  splinter  of  pine  wood  first  dipped  in 
it  and  then  in  strong  nitric  acid  becomes  of  a  blue  color, 
which  then  passes  into  a  brown.  In  many  particulars 
this  substance  resembles  creasote  so  closely,  that  a  suppo- 
sition has  been  entertained  that  they  are  in  reality  the 
same  body. 

When  woody  matter  is  gradually  decomposed  by  con- 
tact with  air  and  moisture,  Ulmine  and  TJhnic  Acid  are 
produced.  They  arise  from  a  partial  oxydation,  attended 
by  the  production  of  carbonic  acid  and  water,  the  action 
being  originally  occasioned  by  azqtized  matter  in  the 
wood  ;  corrosive  sublimate,  or  any  other  body  which  pos- 
sesses the  quality  .of  checking  ferment  action,  may,  there- 
fore, be  resorted  to  to  prevent  the  dry-rot  of  wood.  When 
the  access  of  air  is,  for  the  most  part,  cut  off;  the  brown 
bodies,  ulmine  and  ulmic  acid,  no  longer  appear  alone, 
but  with  them  many  other  substances,  of  the  family  of  the 
hydrocarbons,  arise.  Besides  these,  as  in  the  formation 
of  vegetable  soil  and  turf,  azotized  acids,  such  as  the  Or  en- 
ic  and  Apocrenic,  appear.  These  originate  in  the  decay 
of  the  nitrogenized  constituents  of  the  wood,  an  action 
which  probably  precedes  its  general  disorganization. 
They  are  often  found  in  mineral  springs,  in  combination 
with  oxide  of  iron,  forming  ochery  stains.  Crenic  acid,  by 
exposure  to  the  air,  changes  into  Apocrenic  Acid,  a  sub- 
stance much  less  soluble  in  water. 

There  is  abundant  proof  that  all  the  varieties  of  coal 
have  originated  from  woody  fibre.  For  the  production  ot 
these,  it  seems  requisite  that  the  wood  should  be  immers- 
ed in  water  at  a  moderately  high  temperature,  and  with- 
out free  contact  of  air.  The  ulmine  bodies  form  from  the 
decay  of  wood  at  the  surface  of  the  earth ;  the  coal  bod- 
ies under  a  heavy  pressure.  Of  these  we  have  many  va- 
rieties, differing  much  in  constitution :  Lignite,  which  is 
of  a  brown  color,  and  in  which  the  structure  of  the  wood 

What  substance  does  carbolic  acid  closely  resemble  ?  Under  what  cir- 
cumstances are  ulmine  and  ulmic  acid  produced  ?  What  bodies  may  be 
employed  to  prevent  dry-rot  ?  From  what  bodies  do  crenic  and  apocrenic 
acids  arise?  What  is  the  sonrce  of  the  different  varieties  of  coal  ?  What 
is  lignite  ? 


384  ANIMAL    CHEMISTRY. 

is  more  or  less  perfectly  preserved ;  the  various  forms  of 
Bituminous  Coal,  as  cannel  coal,  Newcastle  coal,  &c. ;  An- 
thracite, which  contains  but  little  hydrogen. 

With  these  more  valuable  natural  products  are  frequent- 
ly found  small  quantities  of  others  of  less  importance,  as 
Ozocherit,  or  fossil  wax  ;  Idrialine,  which  is  isomeric  with 
oil  of  turpentine  ;  Petroleum,  or  Naphtha,  which  in  many 
Eastern  countries  is  collected  in  wells.  It  arises,  proba- 
bly, from  the  decomposition  of  coal  by  the  action  of  the 
natural  heat  of  the  earth. 


LECTURE  LXXXVI. 

ANIMAL  CHEMISTRY. — Equilibrium  of  the  System. — Caus- 
es of  Diminution  and  Increase. — Relation  of  Oxygen  to 
the  Food. — Digestion,  the  Nature  of  it. — Description  of 
the  Process. — Artificial  Digestion. —  Two  great  Varieties 
of  Food. — Nutrition  in  the  Carnivora  and  Graminivora. 
— Routes  of  the  Passage  of  Nutritious  Matter  into  the 
System. 

IN  the  preceding  Lectures  I  have  given  the  descriptive 
history  of  many  of  the  more  important  organic  compounds, 
and  chiefly  those  belonging  to,  or  derived  from,  the  vege- 
table kingdom.  It  remains  now  to  mention  another  class 
which  seems  to  bear  a  closer  relation  to  animal  beings. 
The  appearance  and  destruction  of  these  compounds  lead 
by  ready  steps  to  a  consideration  of  the  physiological  func- 
tions of  the  animal  mechanism. 

There  are  certain  causes  which  tend  constantly  to  change 
the  weight  of  an  adult,  healthy  individual ;  causes  of  in- 
crease and  causes  of  diminution.  Among  the  former  may 
be  mentioned  food,  drinks,  and  atmospheric  air ;  among 
the  latter,  urine,  faeces,  transpired  and  expired  matters. 
And  these,  in  the  course  of  a  year,  amount  to  many  hun- 
dred pounds ;  yet  the  resulting  action  of  the  mechanism 
is  such  that,  at  the  end  of  that  time,  the  weight  remains 
unchanged. 

This  fact,  the  constancy  of  adult  weight,  can,  therefore, 
only  be  explained  by  an  examination  of  the  action  of  the 

What  causes  are  in  operation  tending  to  change  the  weight  of  an  adult 
animal  ?  Mention  some  of  the  causes  of  increase,  and  some  of  diminution 


PROCESS    OF    DIGESTION.  385 

matters  introduced  into  the  interior  of  the  system  on  each 
other,  or  an  examination  of  the  matters  rendered.  What- 
ever is  fit  for  food,  when  burned  in  the  open  air,  with  free 
access  of  oxygen,  must  yield  carbonic  acid,  water,  and 
ammonia ;  and  these,  in  point  of  fact,  are  the  results  of  the 
action  of  the  animal  mechanism.  Oxygen  gas,  introduced 
by  the  respiratory  process  through  the  lungs,  effects  event- 
ually the  destruction  of  the  hydrocarbons  and  nitrogenized 
bodies  which  have  been  introduced  through  the  stomach ; 
and  carbonic  acid,  ammonia,  and  the  vapor  of  water,  or 
substances  in  a  transition  state,  which  tend  eventually  to 
assume  those  forms,  are  the  result.  An  elevated  temper- 
ature must,  as  a  consequence,  be  obtained. 

Before  the  introduction  of  chemical  principles  into  the 
science  of  physiology,  it  was  a  favorite  idea  that  the  ani- 
mal system  possessed  the  peculiarity  of  resisting  the  influ- 
ence of  external  agents.  This  is  an  error*  There  is  no 
essential  difference  between  the  physical  effects  taking 
place  in  the  body  during  life  and  after  death,  nor  is  there 
any  principle  of  resistance  to  external  agents  possessed 
by  living  structures.  The  only  distinction  is,  that  during 
life  the  effete  materials  pass  off  by  appointed  routes — the 
kidneys,  the  lungs,  or  the  skin  ;  and  after  death,  these 
passages  being  closed,  they  accumulate  in  the  interior  of 
the  body. 

The  matters  returned  by  an  animal  to  the  external 
world  are  all  found  to  be  oxydized  bodies,  or  such  as  arise 
from  processes  of  oxydation.  The  result  is,  therefore, 
forced  upon  us  that  the  primitive  action  of  the  mechan 
ism  is  the  oxydation  of  the  food  in  the  system  by  air  which 
has  been  introduced  through  the  lungs. 

The  process  of  digestion  appears  to  be  exclusively  for 
the  object  of  effecting  the  minute  subdivision  of  the  food. 
By  the  action  of  the  teeth  or  other  organs  of  mastication, 
it  is  first  roughly  divided  and  simultaneously  mixed  with 
saliva.  It  is  then  passed  into  the  stomach,  and  in  that  or- 
gan mixes  with  the  gastric  juice,  a  viscid  and  slightly 
acid  body.  This  mixture  is  perfected  by  certain  move- 
ments which  the  food  now  undergoes,  and  under  the  con- 

What  is  the  chemical  nature  of  the  food?  What  gas  is  introduced 
through  the  lungs  1  How  do  -these  act  on  each  other?  Do  animal  struc- 
tures possess  any  power  of  resisting  the  influence  of  external  agents  ? 
Why  do  we  conclude  that  the  oxydation  of  the  food  is  the  principal  effect 
going  on  in  the  system  ?  What  is  the  object  qjf  digestion  f 

K  K 


386  PRODUCTION    OF    CHYLE. 

joint  action  of  the  saliva  and  the  gastric  juice  it  is  totally 
broken  up  into  a  gray,  semifluid,  homogeneous  mass, 
sometimes  acid  and  sometimes  insipid,  of  the  consistency 
of  cream  or  gruel,  called  Chyme.  This  gradually  passes 
out  through  the  pyloric  orifice  of  the  stomach,  and  enters 
the  intestine. 

It  has  been  a  question  whether  artificial  digestion  could 
be  performed,  but  it  now  appears  to  be  universally  ad- 
mitted that  an  acidulated  water,  containing  animal  matter 
in  a  state  of  change,  has  the  power  of  impressing  analo- 
gous changes  on  organized  substances  submitted  to  its  ac- 
tion, just  as  the  gastric  juice,  containing  hydrochloric  or 
acetic  acid,  with  animal  matter  undergoing  metamorpho- 
sis, derived  from  the  saliva  or  the  coats  of  the  stomach, 
possesses  the  power  of  dissolving  fibrine  or  coagulated 
albumen. 

Soon  after  its  entrance  into  the  intestine  the  chyme  is 
mingled  with  bile  and  pancreatic  juice,  the  former  com- 
ing from  the  liver,  the  latter  from  the  pancreas.  The  ef- 
fect appears  to  be  a  division  of  the  chyme  into  three 
parts :  1st.  A  creamy  fluid ;  2d.  A  whey-like  fluid ;  3d. 
A  red  sediment:  the  two  former,  commingled,  consti- 
tute what  is  designated  the  Chyle. 

It  has  been  already  remarked  that  the  aim  of  the  di- 
gestive process  appears  to  be  the  subdivision  of  the  food. 
It  is  for  this  that  the  teeth  comminute  it ;  and  the  gastric 
juice,  excited  to  activity  by  the  oxygen  introduced  with 
the  saliva,  breaks  down  by  its  ferment  action  all  albumi- 
nous and  fibrinous  matters,  and  prepares  the  food,  in  this 
condition  of  extreme  subdivision,  for  its  passage  into  the 
blood-vessels. 

Before  we  can  trace  the  changes  which  then  occur,  it 
is  proper,  however,  to  remark  that,  as  respects  the  food 
itself,  it  may  be  distinguished  into  two  varieties :  1st.  The 
food  of  nutrition,  or  the  nitrogenized  food ;  2d.  The  food 
of  respiration,  or  the  non-nitrogenized  food. 

The  nutritive  processes  of  carnivorous  animals  are  very 
simple ;  they  live  on  the  graminivora,  and  find,  in  the  car- 
cases they  consume,  the  fats,  the  fibrine,  and  other  such 

How  is  the  chyme  prepared  ?  Can  digestion  be  conducted  artificially  ? 
With  what  fluids  does  the  chyme  mingle  ?  "What  is  their  action  on  it? 
What  is  chyle  ?  What  two  great  varieties  of  food  are  there  ?  Describe 
the  nutritive  processes  of  the  carnivora. 


ORIGIN    OF    FAT.  387 

bodies  which  are  necessary  for  their  own  economy;  these, 
therefore,  simply  require  to  be  brought  into  a  state  of  so- 
lution, or  of  extreme  subdivision,  and  then  are  absorbed 
into  the  blood-vessels.  In  these  cases  the  fats  constitute 
the  food  of  respiration,  and  the  nitrogenized  bodies  that 
of  nutrition. 

But  the  graminivora  find  in  the  vegetable  matters  they 
use  the  same  essential  principles ;  their  fibrine,  albumen, 
and  fats  are  directly  obtained  from  plants,  in  which  they 
naturally  occur.  In  the  digestive  process  of  the  two 
great  classes  of  animals,  there  is  not  therefore,  in  reality, 
any  difference ;  both  find  in  their  food  the  elements  they 
require. 

There  is  reason  for  believing  that  the  two  classes  of 
food  are  introduced  into  the  system  by  different  routes— 
the  fatty  or  respiratory  food  passing  through  the  lacteals, 
and  the  nitrogenized  bodies  being  taken  up  by  the  veins. 


LECTURE  LXXXVIL 

ORIGIN  AND  DEPOSITS  OF  THE  FATS  AND  NEUTRAL  NI- 
TROGENIZED BODIES. — Artificial  Formation  of  Fat. — It 
may  be  made  in  the  Animal  System,  or  directly  absorbed 
from  the  Food.- — Proofs  of  the  latter. — -Varieties  of  Fat 
arising  in  partial  Oxydation. — Changes  in  Fat  as  it 
passes  through  the  Systems  of  the  Graminivora  and 
Carnivora.  —  Its  final  Destruction. —  Origin  and  De- 
posit of  the  Neutral  Nitrogenized  Bodies. — Properties 
of  Fibrine i  Albumen,  Caseine,  Proteine,  Gelatine,  &c. 

Two  opinions  have  been  entertained  respecting  the 
origin  of  the  fat  which  occurs  in  the  adipose  tissues  of 
animals.  1st.  It  has  been  supposed  to  be  produced  by 

Erocesses  taking  effect  in  the  system  ;  or,  2d.  Simply  col- 
3Cted  from  the  food. 

In  many  various  processes  fatty  bodies  arise.  Thus, 
when  flesh  meat  is  left  in  a  stream  of  water,  a  mass  of 
adipocire  is  eventually  found.  During  the  action  of  nitric 
acid  on  fibrine,  and  in  the  preparation  of  oxalic  acid  from 

What  is  their  respiratory  food  ?  Describe  the  nutritive  processes  of  the 
graminivora.  By  what  routes  are  the  two  varieties  of  food  introduced  into 
the  system  1  What  opinions  have  been  held  respecting  the  origin  of  fat  ? 
In  what  processes  is  it  apparently  produced  ? 


388  ABSORPTION    OF    FAT. 

starch,  oily  "bodies  are  apparently  produced.  There  is 
every  reason  to  believe,  however,  that  these  are  rather 
insulated  than  formed,  or  that  they  pre-exist  in  the  bodies 
from  which  they  are  apparently  derived. 

But  recent  experiments,  as  in  the  preparation  of  bu- 
tyric acid  from  sugar,  have  decisively  demonstrated  that 
the  fatty  bodies  can  be  artificially  formed  from  the  non- 
nitrogenized  by  processes  such  as  those  of  fermentation, 
and,  consequently,  we  have  every  reason  to  suppose  that 
the  animal  system  can  form  fats  from  the  food,  although 
none  might  occur  there  naturally. 

But  though  the  power  of  forming  oily  from  amyla- 
ceous bodies  maybe  possessed  by  the  animal  mechanism, 
there  can  be  no  doubt  that  in  many  instances  it  is  not  re- 
sort'ed  to,  and  that  fats  contained  in  the  food  are  at  once 
absorbed  into  the  system.  Often  this  absorption  takes 
place  with  so  slight  a  change  impressed  upon  the  oil,  that 
without  difficulty  we  can  detect  its  presence  by  its  odor 
or  its  taste.  Thus,  the  milk  of  cows  which  are  fed  on 
linseed  cake  tastes  strongly  of  that  substance ;  and  at 
those  seasons  of  the  year  when  such  animals  feed  on 
young  shoots  or  leaves  containing  odoriferous  oils,  the 
taste  is  at  once  detected  in  the  milk. 

The  deposition  of  fat  upon  an  animal,  and  the  produc- 
tion of  butter  in  its  milk,  bear  a  certain  relation  to  the 
amount  of  oleaginous  matters  found  in  its  food.  For  this 
reason,  Indian  corn,  which  contains  from  eight  to  twelve 
per  cent,  of  oil,  furnishes  one  of  the  most  available  arti- 
cles for  feeding  and  fattening  cattle.  It  is  now,  however, 
admitted  that  where  foods  without  fat  are  used,  the  sys- 
tem possesses  the  power  of  effecting  their  production ; 
thus,  bees  will  produce  wax  though  fed  upon  pure  sugar, 
and  animals  will  grow  fat  though  fed  on  potatoes  alone. 

A  great  nulnber  of  the  fatty  bodies  may  be  derived 
from  margaric  acid  by  processes  of  partial  oxydation. 
With  a  limited  supply  of  oxygen  gas,  ethalic  and  myris- 
tic  first  make  their  appearance  ;  and  the  supply  being  still 
continued,  there  follow  cocinic,  lauric,  &c.,  the  process 
being  as  shown  in  the  following  table  : 

"What  reason  is  there  to  believe  that  it  can  be  formed  from  the  starch 
bodies  ?  Wnat  reason  is  there  for  believing  that  many  fats  are  directly 
absorbed  into  the  system  ?  Is  there  any  relation  between  the  production 
of  butter  and  the  quantity  of  oil  in  the  food  ?  Can  bees  form  wax  from 
sugar  ?  By  what  process  can  the  fatty  bodies  be  derived  from  each  other  ? 


PARTIAL    OXYDATION    OF    FAT.  389 


Margaric. 
Ethalic. 
My  ri  stic. 
Cocinic. 
L  auric. 


Capric. 

(Enanthytic. 

Caproic. 

Valerianic. 

Butyric. 


These  partial  oxydations  being  perfected,  there  result  at 
last  carbonic  acid  gas  and  water,  the  same  bodies  which 
appear  when  a  fat  is  directly  burned  in  the  open  atmos- 
pheric air. 

The  fats  which  occur  in  plants  pass  into  the  systems  of 
graminivorous  animals,  and  there  undergo  changes,  a  se- 
ries of  partial  oxydations  occurring.  It  is  only  a  part 
which  is  completely  destroyed  so  as  to  produce  carbonic 
acid  and  water,  and  this  part  is  the  element  of  respiration. 
The  residue  accumulates  in  the  cells  of  the  adipose  tis- 
sues, and,  devoured  by  the  carnivorous  tribes,  is  destined 
to  undergo  in  them  those  successive  changes  which  bring 
it  back  to  the  condition  of  carbonic  acid  and  water,  and 
restore  it  to  the  atmosphere  from  which  it  was  originally 
derived  by  plants. 

The  amylaceous  bodies  and  fats,  or  the  non-nitrogenized 
bodies,  are,  therefore,  the  food  of  respiration ;  their  office 
is  to  neutralize  the  oxygen  introduced  by  the  lungs,  and, 
by  the  production  of  carbonic  acid  gas  and  water,  keep 
up  the  temperature  of  the  animal  system. 

I  have  already  described  the  fatty  bodie's,  and  given  the 
history  of  their  general  properties.  It  is  unnecessary  to 
repeat  here  what  has  been  already  said. 

When  the  expressed  juices  of  plants,  such  as  beets,  tur- 
nips, &c.,  are  allowed  to  stand,  there  is  deposited,  after  a 
short  time,  a  coagulum  or  clot,  which  does  not  appear  to 
differ  in  any  respect  from  animal  Fibrine.  If  this  be  remov- 
ed, and  the  temperature  of  the  juice  raised  to  212°  F.,  it 
becomes  turbid  again,  from  the  deposit  of  a  second  body, 
Albumen.  On  separating  this  and  slowly  evaporating,  a  film 
forms  on  the  surface,  identical  with  Caseine.  These  three 
bodies  contain  nitrogen,  and  may,  therefore,  be  looked  upon 
as  the  representatives  of  the  neutral  nitrogenized  class. 

Fibrine  (C^H^O^N^  .  -f  (S.P)  ). — This  substance  may 
be  obtained  by  beating  fresh-drawn  blood  with  twigs,  and 

In  what  do  these  partial  oxydations  terminate  at  last  ?  What  change 
occurs  to  vegetable  fats  in  passing  through  the  systems  of  the  graminivora? 
What  is  the  object  of  the  entire  combustion  of  a  portion  of  it  ?  By  what 
means  is  the  residue  at  last  brought  to  the  same^tate?  What  bodies 
constitute  the  food  of  respiration  ?  What  is  the  composition  of  fibrine  1 

K.K2 


390  FIBRINE. ALBUMEN. CASEINE. 

washing  with  water  and  ether  the  clot  which  adheres 
thereto.  As  thus  prepared,  fibrine  is  a  white,  elastic 
body,  insoluble  in  water,  alcohol,  or  ether,  but  soluble  in 
hydrochloric  acid,  with  which  it  yields  a  blue  solution. 
It  possesses  the  power  of  decomposing  rapidly  the  deu- 
toxide  of  hydrogen.  When  dried  it  shrinks  very  much  in 
volume,  but,  for  the  most  part,  recovers  its  bulk  when 
again  moistened.  Fibrine  derived  from  arterial  and  ve- 
nous blood  is  not  altogether  the  same  ;  the  latter  may  be 
dissolved  in  a  warm  solution  of  nitrate  of  potash,  but  the 
former  can  not.  In  the  formula  annexed  to  this  body, 
the  symbols  within  the  brackets  merely  mean  small  and 
indeterminate  quantities  of  sulphur  and  phosphorus. 

Albumen  occurs  abundantly  in  the  serum  of  blood  and 
in  the  white  of  eggs,  from  which  it  may  be  obtained  by 
neutralizing  in  a  solution  of  it  the  associated  soda  with  ace- 
tic acid,  and  on  dilution  with  cold  water  it  falls  as  a  white 
precipitate,  soluble  in  water  containing  a  minute  quantity 
of  alkali.  Exposed  to  a  sufficient  heat,  common  albumen 
coagulates  and  becomes  a  white  body,  wholly  insoluble  in 
water.  The  strong  acids  also  unite  directly  with  it,  and 
form  insoluble  compounds  ;  acetic  and  the  tribasic  phos- 
phoric acid  are  exceptions.  With  metallic  salts,  as  cor- 
rosive sublimate,  it  gives  insoluble  precipitates ;  hence  its 
use  as  an  antidote  for  that  poison.  Its  constitution  is  iden- 
tical with  that  of  fibrine,  except  that  it  appears  to  contain 
twice  as  much  sulphur. 

Caseine  is  found  abundantly  in  milk.  It  is  insoluble  in 
water,  but,  like  albumen,  is  readily  dissolved  if  free  al- 
kali is  present.  It  may  be  obtained  by  coagulating  milk 
with  sulphuric  acid,  and  dissolving  the  curd,  after  it  has 
been  well  washed  with  water,  in  a  solution  of  carbonate 
of  soda.  By  standing  it  separates  into  two  portions,  oily 
and  watery.  From  the  latter  the  caseine  is  re-precipitated 
by  sulphuric  acid,  and  the  process  repeated.  The  caseine 
is  finally  washed  with  ether  to  remove  any  trace  of  fat. 
It  is  a  white  substance,  soluble  in  an  alkaline  water,  the  so- 
lution not  being  coagulated  by  boiling,  but  a  skin  forms 
on  the  surface  as  evaporation  goes  on.  It  can,  however, 
be  coagulated  by  certain  animal  membranes,  as  by  the 

From  what  sources  may  it  be  derived?  What  are  its  properties? 
What  are  the  sources  and  properties  of  albumen  ?  What  are  the  sources 
«md  properties  of  caseine  ? 


PROTEINB    AND    ITS    DERIVATIVES.  391 

interior  coat  of  the  stomach  of  a  calf.  It  contains  five  or 
six  per  cent,  of  bone  earth. 

The  foregoing  bodies  are  sometimes  spoken  of  as  the 
PROTEINE  group,  from  the  circumstance,  as  is  shown  in 
their  formula,  that  they  all  contain  C48JHr36OuAr6,  a  body 
which  passes  under  the  designation  of  proteine.  It  may 
be  extracted  from  them  by  dissolving  either  of  them  in  an 
alkaline  solution,  and  precipitating  by  an  acid.  It  is  a 
tasteless,  white,  insoluble  body,  soluble  in  acetic  acid 
and  in  alkalies.  It  yields  a  binoxide  and  tritoxide,  which 
may  be  produced  by  boiling  fibrine  in  water  in  contact 
with  air.  These  substances  are  the  chief  constituents  of 
the  buff"y  coat  of  inflammatory  blood. 

Gelatine  (C13H10N2O5)  is  prepared  by  dissolving  isin- 
glass in  warm  water.  It  forms,  on  cooling,  a  soft  jelly, 
which  contracts  as  it  dries.  Solution  of  gelatine  is  pre- 
cipitated by  corrosive  sublimate,  tannic  acid,  or  infusion 
of  galls  ;  with  the  latter  bodies  it  yields  a  precipitate 
which  is  the  basis  of  leather.  Glue  is  an  impure  gelatine. 

On  examining  the  constitution  of  some  of  the  leading 
tissues  of  the  animal  system,  it  is  plain  that  they  bear  a 
remarkable  relation  to  proteine,  as  is  shown  in  the  fol- 
lowing table : 

Proteine,  C<&HzsN&Ou .    .    .    .  =   Pr. 

Arterial  membrane =   Pr  -4-   HO. 

Chondrihe  (rib  cartilage)    .    .    .  =    Pr  4-    HO  -4-  O. 

Hair,,horns =    Pr  -f    NH34-O3. 

Gelatinous  tissues =  2Pr  -j-  3NH3  -j-  HO  -f-  Or. 

These  different  bodies  are,  therefore,  derived  from  the 
proteine  group  by  processes  of  partial  oxydation ;  for  in 
their  constitution  they  correspond  to  oxides,  hydrated  ox- 
ides, &c. 

The  nitrogenized  bodies  introduced  into  the  system 
pass  through  the  same  changes  as  the  non-nitrogenized : 
partial  oxydations  giving  rise  to  various  tissue  forms,  and 
ending  in  perfect  oxydation,  with  a  production  of  water, 
ammonia,  and  carbonic  acid. 

Whether  we  regard  the  respiratory  or  the  nutritive 
food,  we  see  that  the  result  is  the  same.  Introduced 
through  the  blood-vessels  into  the  system,  it  is  brought 

"What  is  proteine  ?  What  relation  has  it  to  the  foregoing  bodies  ?  What 
oxides  does  it  give  ?  How  is  gelatine  obtained  ?  What  precipitate  does 
it  give  with  infusion  of  galls  ?  What  relation  does  proteine  bear  to  other 
tissue  bodies  1  What  changes  do  the  nitrogenized  bodies  pass  through  ? 


392  ENTRANCE    OF    FOOD    INTO    THE    SYSTEM. 

under  the  destructive  influence  of  oxygen  arriving  through 
the  lungs,  and,  as  I  have  already  explained,  the  amount 
of  oxygen  is  so  adjusted  to  the  amount  of  these  classes  of 
food  combined,  that  in  an  adult  and  healthy  individual  the 
weight  does  not  change,  even  after  the  lapse  of  a  consid- 
erable period  of  time. 


LECTURE  LXXXVIII. 

OF  THE  INTRODUCTION  OF  RESPIRATORY  AND  NUTRITIOUS 
FOOD  INTO  THE  BLOOD,  AND  ITS  TRANSMISSION  THROUGH 
THE  SYSTEM. — Absorption  by  the  Lacteals  and  Veins. — 
Cause  of  the  Circulation  of  the  Blood. — Constitution  and 
Properties  of  the  Blood. — Plasma  and  Disks. —  The  Of- 
fices of  each. —  The  Coagulation  of  Blood. — Analysis 
of  Blood. 

THE  ordinary  principles  of  capillary  attraction  are  am- 
ply sufficient  to  account  for  the  absorption  of  nutritious 
matter  from  the  intestinal  cavity,  both  by  the  lacteal  ves- 
sels and  the  veins.  By  this  it  is  eventually  brought  into 
the  general  current  of  the  circulation,  and  distributed  to 
every  part  of  the  system. 

With  respect  to  the  forces  involved  in  the  circulation 
of  the  blood,,  most  physiologists  have  regarded  the  hy- 
draulic action  of  the  heart  as  amply  sufficient  to  account 
for  all  the  phenomena.  It  is  now  on  all  hands  conceded 
that  this  organ  discharges  a  very  subsidiary  duty.  The 
whole  vegetable  creation,  in  which  circulatory  movements 
of  liquids  are  actively  carried  on  without  any  such  central 
mechanism  of  impulsion;  the  numberless  existing  acar- 
diac  beings  belonging  to  the  animal  world ;  the  accom- 
plishment of  the  systemic  circulation  of  fishes  without  a 
heart ;  and  the  occurrence  in  the  highest  tribes,  as  in  man, 
of  special  circulations  which  are  isolated  from  the  greater 
one,  have  all  served  to  demonstrate  that  we  must  look  to 
other  principles  for  the  cause  of  these  remarkable  move- 
ments. 

The  cause'  of  the  circulation  of  the  blood  is  to  be  found 

What  physical  principle  is  involved  in  the  absorbent  action  of  the  lac- 
teals  and  veins  ?  What  reasons  are  there  for  supposing  that  the  action  of 
the  heart  ia  not  the  Only-cause  of  the  tirculation  ? 


CIRCULATION    OF    THE    BLOOD.  393 

in  the  chemical  relations  of  that  liquid  to  the  tissues  with 
which  it  is  brought  in  contact.  On  the  principles  of  ca- 
pillary attraction  a  liquid  will  readily  flow  through  a  por- 
ous body  for  which  it  has  a  chemical  affinity,  but  it  will 
refuse  to  flow  through  it  if  it  has  no  affinity  for  it.  On 
this  principle  we  can  easily  explain  why  the  arterial  blood 
presses  the  venous  before  it  in  the  systemic  circulation, 
and  why  the  reverse  ensues  in  the  pulmonary.  This  ex- 
planation of  the  circulation  of  the  blood,  whicji  I  offered 
some  years  ago,  is  now  admitted  by  many  of  the  leading 
physiological  writers  to  be  true. 

The  systemic  circulation  takes  place  because  arterial 
blood  has  a  high  affinity  for  the  tissues,  and  venous  blood 
little  or  none.  The  pulmonary  circulation  takes  place 
because  venous  blood  has  a  high  affinity  for  atmospheric 
oxygen,  which  it  finds  on  the  air  cells  of  the  lungs,  and  ar- 
terial blood  little  or  none.  On  the  same  principle  we  may 
explain  the  rise  of  sap  in  trees,  the  circulatory  movements 
in  the  different  animal  tribes,  and  the  minor  circulations 
of  the  human  system. 

The  most  striking  peculiarity  of  the  blood  is  the  inces- 
sant change  which  it  undergoes.  It  is  constantly  being 
destroyed,  and  as  constantly  being  reproduced.  It  con- 
sists of  two  portions,  the  Plasma,  a  clear  fluid,  of  a  yellow- 
ish tinge,  which  contains  fibrine,  albumen,  and  fat ;  and 
in  this  there  float  disk-like  bodies  of  different  shapes  and 
magnitudes  in  different  animals.  In  man  they  are  about 
__'__  of  an  inch  in  diameter,  consist  of  a  sac  of  Globuline, 
a  body  of  the  proteine  family,  and  in  the  interior  they  con- 
tain a  red  substance,  Hcematine,  which  gives  them  their 
peculiar  color.  On  one  portion  of  them  there  is  a  nucle- 
us or  speck,  consisting  of  coagulated  fibrine.  When  the 
disks  are  old  and  about  to  be  destroyed,  their  interior  is 
filled  with  Hcemapkem,  a  yellow  substance,  correspond- 
ing to  the  coloring  matter  of  the  urine.  Besides  these, 
there  are  lymph,  chyle,  and  oil  globules  in  the  blood. 

A  continuous  metamorphosis  goes  on  during  the  circu- 
lation of  the  blood ;  the  plasma  serves  for  the  purposes 

What  explanation  may  be  given  of  the  circulation  in  the  capillaries  ? 
What  is  the  cause  of  the  systemic  circulation  ?  What  of  the  pulmonary  ? 
Of  what  parts  is  the  blood  composed  ?  What  are  the  properties  of  the 
plasma  ?  Of  what  are  the  disks  composed  ?  What  are  globuline.  hrema- 
tine,  and  hasmaphein  ?  What  are  the  functions  of  the  plasma  and  disks 
respectively  1 


394  COAGULATION    OF    BLOOD. 

of  nutrition,  the  disks  for  the  production  of  heat.  They 
absorb  oxygen  in  the  air  cells  of  the  lungs,  and  transmit 
it  to  all  parts  of  the  system ;  and  as  they  grow  old  and 
disappear,  new  ones  are  formed  from  the  plasma. 

Although  fibrine  is  known  to  exist  in  plants,  I  doubt  very 
much  whether  it  is  directly  absorbed  as  Fibrine  into  the 
system.  Besides  the  direct  proof  which  we  have  from 
the  analysis  of  those  bodies,  we  know  that  fibrine  and  al- 
bumen so  .closely  resemble  each  other  in  constitution  that 
they  are  mutually  convertible  into  each  other.  During 
the  hatching  of  an  egg  from  its  albumen  the  flesh  (fibrine) 
of  the  young  chicken  is  formed,  a  phenomenon  accom- 
panying the  absorption  of  oxygen  from  the  air.  In  the 
human  system,  abundant  observation  has  proved  that 
there  is  a  direct  connection  between  the  quantity  of  oxy- 
gen introduced  through  the  lungs  and  the  amount  of  fibrine 
in  the  blood.  When  the  respiratory  process  is  unduly 
active  the  disks  oxydize  with  rapidity,  and  the  amount  of 
fibrine  increases  ;  but  when  the  reverse  takes  place,  there 
is  a  restraint  on  the  change  of  the  disks,  and  the  amount 
of  fibrine  declines. 

The  coagulation  of  the  blood  is  a  phenomenon  which 
has  excited  much  attention,  physiologists  generally  look- 
ing upon  it  either  as  wholly  inexplicable,  or  what,  in  re- 
ality, amounts  to  the  same  thing,  as  due  to  the  death  of 
the  blood.  What  connection  there  is  between  its  life  and 
fluidity,  is  not  so  very  apparent.  A  little  reflection  will,  I 
am  persuaded,  deprive  this  phenomenon  of  much  of  its 
fictitious  importance,  since  it  is  plain  that  the  coagulation 
of  the  blood,  or,  in  other  words,  the  separation  of  fibrine 
from  it  takes  place  in  the  body  as  well  as  out  of  it,  for  from 
this  coagulated  fibrine  the  muscular  tissues  are  formed, 
and  from  it  their  waste  is  repaired.  By  passing  through 
two  capillary  circulations,  the  systemic  and  the  pulmona- 
ry, the  rapidity  of  the  process  is  very  much  interfered 
with ;  but  still,  it  eventually  takes  place. 

I  here  insert  one  of  Lecanu's  analyses  of  the  blood  ;  it 
may  serve  to  give  an  idea  of  the  constitution  of  that  liquid. 
It  must  not  be  forgotten,  however,  that  such  analyses,  be- 
yond mere  general  results,  are  of  little  value ;  the  compo- 

What  reasons  are  there  for  supposing1  that  fibrine  may  be  made  in  the 
system  from  albumen  or  caseine  ?  -  Does  the  coagulation  of  the  blood  take 
place  during  life  ?  Of  what  are  the  muscular  tissues  composed  T 


PROCESSES  OF  SECRETION.  395 

•sition  of  the  blood  varies  incessantly  in  the  same  individ- 
ual. For  instance,  the  mere  accident  of  his  being  thirsty, 
or  having  recently  drank  abundantly  of  water,  will  make 
an  entire  change  in  the  analysis  of  the  blood. 

Water  .     ...     * 780'145. 

Fibrine .         .      2*100. 

Coloring  matter 133-000. 

Albumen 65-090. 

Crystalline  fatty  matter. 2'430. 

Oily  matter 1-310. 

Extractive  matter 1-790. 

Salts  and  loss 14-135. 

1000-000. 

The  following  represents  the  constitution  of  haemato- 
sine : 

Carbon -.    .    66-49. 

Hydrogen 5'30. 

Nitrogen .     10-50. 

Oxygen 11-05. 

Iron 6-66. 

100-00. 


LECTURE  LXXXIX. 

NATURE  OP  THE  PROCESSES  OP  SECRETION. — Origin  of 
Secretions. —  Phenomena  of  Respiration. — Arterializa- 
tion. — Production  of  Animal  Heat. — Removal  of  effete 
Matters. — Constitution  of  Milk. —  Uses  of  that  Secretion. 
— Mucus.- — Pus. —  Bile, —  Urine. —  Calculi. —  Bones. — 
Nervous  Matter. 

DURING  the  starvation  of  an  animal  all  its  various  se- 
cretions are  still  formed  :  a  consideration  which  proves 
that  the  production  of  urine,  bile,  and  other  such  bodies 
is,  in  reality,  connected  with  the  destructive  processes 
going  on  in  the  animal  system.  These  processes  of  de- 
cay originate  in  the  action  of  oxygen  admitted  by  the 
process  of  respiration. 

The  lungs,  which  constitute  the  organ  by  which  air  is 
introduced,  are  originally  developed  as  diverticula  from 
the  oesophagus,  and  finally  become  an  immense  congeries 
of  cells  emptying  into  the  trachea.  In  respiration  they 
are  perfectly  passive,  the  air  being  introduced  and  ex- 

What  circumstances  tend  to  change  the  constitution  of  the  blood  ?  How 
is  it  known  that  the  secretions  arise  from  destructive  processes  ?  What 
is  the  structure  of  the  lungs  ? 


396  ARTERIALIZAT10N    OF    BLOOD. 

pelled  alternately  by  muscular  contraction.  It  is  com-* 
monly  estimated  that,  on  an  average,  about  17  inspira- 
tions are  made  each  minute,  and  at  each  inspiration  about 
17  cubic  inches  of  air  are  introduced. 

The  blood  presents  itself  on  the  air  cells  of  a  deep  blue 
color,  and  is  then  known  as  venous  blood.  Through  the 
thin  wall  of  the  cell  it  obtains  oxygen  from  the  air,  and 
gives  out  carbonic  acid.  It  is  the  coloring  matter  of 
the  disks  which  discharges  this  function,  and  during  the 
act  of  change  its  tint  alters  to  a  bright  crimson.  It  is 
said  now  to  be  arterialized,  or  to  constitute  arterial  blood. 
The  magnitude  of  the  scale  on  which  this  operation  is 
carried  forward  may  be  appreciated  from  the  circum- 
stance that  in  a  man  of  average  size,  in  a  single  day,  about 
seven  tons  of  blood  have  been  exposed  to  226  cubic  feet 
of  atmospheric  air. 

The  oxygen  thus  introduced  acts  directly  either  on 
the  tissues  themselves,  as  it  is  distributed  by  the  systemic 
circulation,  or  on  the  elements  of  respiration  they  con- 
tain. In  the  latter  case,  carbonic  acid  gas  and  water  are 
the  result ;  in  the  former,  carbonic  acid,  water,  and  am- 
monia. But  these  changes  can  not  take  place  without  an 
elevation  of  temperature.  Carbon  and  hydrogen  can  nei- 
ther burn  in  the  air  nor  in  the  animal  system  without 
evolving  heat.  The  high  temperature  which  an  animal 
can  maintain  is,  therefore,  directly  proportional  to  the 
quantity  of  oxygen  it  consumes. 

The  tissues  being  thus  acted  upon,  give  rise,  during 
their  metamorphoses,  to  new  products,  which  require  to  be 
removed  from  the  system  ;  these,  passing  under  the  name 
of  secretions,  are  discharged  by  glands  or  other  special 
organs.  Thus,  the  carbonic  acid,  for  the  most  part,  es- 
capes from  the  lungs  ;  the  ammonia  through  the  kidneys ; 
the  water  through  both  those  organs  and  the  skin.  Lie- 
big  has  attempted  to  show  that  if  the  elements  of  urine 
be  added  to  the  elements  of  bile,  they  will  represent  the 
elements  in  the  blood ;  and  there  can  be  no  doubt  that 

How  many  inspirations  does  a  man  make,  on  an  average,  in  a  minute  ? 
How  many  cubic  inches  of  .air  are  introduced  at  each  inspiration  1  What 
is  meant  by  the  arterialization  of  the  blood  ?  What  action  does  the  oxy- 
gen introduced  exert  ?  In  what  does  animal  heat  arise  ?  Through  what 
channels  are  the  leading  secretions,  water,  ammonia,  and  carbonic  acid, 
discharged  ?  What  supposed  relation  is  there  between  the  constituents 
of  the  urine  and  bile  conjointly  and  those  of  the  blood  ' 


NUTRITION    OF    MILK.  397 

the  sulphates  and  phosphates  found  in  the  urine  arise  di- 
rectly from  the  sulphur  and  phosphorus  previously  exist- 
ing in  the  muscular  fibre  and  nervous  matter. 

As  an  illustration  of  the  principles  here  given  in  rela- 
tion to  the  functions  of  nutrition  and  secretion,  the  con- 
stitution and  properties  of  milk  may  be  cited.  The  fol- 
lowing is  an  analysis  of  it : 

Water .         -     ...  873-00 

Butter .     30-00. 

•       ,          Caseine ...'...     48-20. 

Milk  sugar 43-90. 

Phosphate  of  lime 2'31. 

"  "  magnesia     ......        '42. 

"  "  iron .        -07. 

Chloride  of  potassium 1-44. 

"          "  sodium i    •    •?**      '24- 

Soda  in  combination  with  caseine      .     .        '42. 


1000-00. 

Of  the  substances  here  mentioned,  all  are  undoubtedly 
obtained  directly  from  the  food.  In.  the  herbage  on 
which  a  graminivorous,  milk-giving  animal  feeds,  every 
one  of  these  constituents  occurs.  I  have  already  shown 
that  the  butter,  or  fat,  and  the  caseine  are  thus  directly  de- 
rived, and  the  evidence  is  equally  complete  ttyat  all  the 
salts  of  phosphoric  acid  and  chlorine  arise  from  the  same 
source. 

A  young  animal,  which,  in  the  first  periods  of  its  life,  is 
nourished  exclusively  on  milk,  finds  in  that  milk  all  the 
various  compounds  it  requires  for  its  own  existence  and 
growth.  The  respiratory  food  is  there — it  is  the  butter 
and  rn^ilk  sugar ;  the  nitrogenized  food  is  there — it  is  the 
caseine ;  and  we  have  already  seen  that  albumen  and 
caseine  are  both  convertible  into  fibrine  ;  the  caseine,  thus, 
in  the  mother's  milk,  becomes  converted  into  flesh  in  the 
young  animal.  To  insure  the  growth  of  its  bones,  phos- 
phate of  lime  (bone  earth)  is  present ;  there  is  also  chlo- 
rine to  form  the  hydrochloric  acid  of  its  gastric  juice,  and 
soda,  which  is  an  essential  ingredient  in  its  bile. 

It  remains  now  to  add  a  brief  description  of  the  prop- 
erties of  the  remaining  leading  animal  substances,  among 
which  may  be  mentioned : 

From  what  do  the  sulphates  and  phosphates  of  the  urine  arise  ?    What 
are  the  chief  constituents  of  milk  ?    From  what  source  are  they  derived  ? 
What  becomes  of  the  butter,  milk  sugar,  caseine,  phosphate  of  lime,  chlo- 
rine, and  soda  in  the  body  of  the  young  animal  ? 
L  L 


CHYLE. BILE. URINE. 

CHYLE  is  usually  of  a  white  or  reddish  white  tint.  It 
resembles  blood  in  constitution  and  power  of  coagulat- 
ing. It  contains  much  fat,  which  gives  to  it  a  cream-like 
aspect. 

Mucus  exudes  from  the  surface  of  mucous  membranes. 
It  is  of  a  white  or  yellow  color,  of  a  viscid  constitution, 
and  insoluble  in  water.  It  dissolves  in  a  solution  of  pot- 
ash, and  is  precipitated  by  an  alkali. 

Pus,  a  secretion  from  injured  surfaces,  resembling  mu- 
cus in  many  respects,  but  distinguished  by  not  being  sol- 
uble in  potash  solution,  but  converted  by  it  into  a  gelat- 
inous body,  which  can  be  pulled  out  in  threads. 

BILE,  a  yellow  liquid,  secreted  by  the  liver  from  the 
portal  blood ;  it  turns  green  in  the  air,  has  a  bitter  taste 
and  an  alkaline  reaction,  due  to  the  presence  of  soda.  Its 
coloring  matter  is  chlorophyl.  It  is  regarded  as  a 
choleate  of  soda,  the  constitution  of  choleic  acid  being 
C76He&NzO2.2.  Of  the  correctness  of  this  formula  there  is 
considerable  doubt,  since  it  has  been  recently  affirmed 
that  Taurine,  which  is  a  derivative  body,  contains  a  large 
amount  of  sulphur. 

URINE,  a  yellow -colored  fluid,  secreted  by  the  kid- 
neys ;  has  an  acid  reaction  ;  its  specific  gravity  from  1/005 
to  1*030 ;  putrefies  at  a  moderate  temperature,  its  urea 
passing  into  the  condition  of  carbonate  of  ammonia.  The 
chief  constituents  of  urine  are  urea,  uric  acid,  the  sul- 
phates and  phosphates  of  potash,  soda,  lime,  ammonia, 
and  a  yellow  coloring  matter,  with  mucus  of  the  bladder. 

The  constitution  of  the  urine  changes  in  diseasfe.  In 
Diabetes  it  contains  grape  sugar,  as  may  be  shown  by  the 
test  of  sulphate  of  copper,  already  mentioned.  Diabetic 
urine  may  even  be  fermented  with  yeast,  and  alcohol  dis- 
tilled from  it. 

URINARY  CALCULI  are  stony  concretions  often  formed 
in  the  bladder  of  man  and  many  animals  ;  they  are  of  dif- 
ferent kinds :  1st.  Uric  acid^  2d.  Urate  of  ammonia.  3d. 
Phosphate  of  lime,  magnesia,  and  ammonia.  4th.  Ox- 
alate  of  lime,  or  mulberry  calculus.  5th.  Cystic  and  xan- 
thic  oxides. 

What  is  chyle  ?  What  is  mucus  ?  How  may  pus  be  distinguished  from 
mucus  ?  What  are  the  chief  properties  of.bile  1  From  what  is  it  formed  ? 
What  does  taurine  contain  ?  What  are  the  chief  constituents  of  urine  ? 
How  may  sugar  be  detected  in  diabetic  urine  ?  What  varieties  of  uri- 
nary calculi  are  there  ? 


NERVOUS    MATTER.  399 

BONES  consist  of  two  parts :  an  animal  and  an  earthy 
matter.  The  latter  is  the  phosphate  of  lime  (bone  earth). 

NERVOUS  MATTER  consists  of  an  albuminous  substance 
with  several  fatty  principles,  distinguished  by  the  remark- 
able fact  that  they  contain  phosphorus.  In  addition,  it 
contains  chlolesterine. 

It  would  not  agree  with  the  object  of  these  Lectures 
were  I  here  to  offer  any  detailed  remarks  on  the  func- 
tions of  the  brain  and  the  nervous  system.  Of  the  action 
of  the  lungs,  the  liver,  the  kidneys,  or  other  such  organs, 
we  are  beginning  to  have  a  very  distinct  idea ;  but  it  is 
altogether  different  with  the  functions  of  the  cerebro-spi- 
nal  axis ;  there  every  thing  is  in  mystery  and  darkness  ; 
yet  it  is  in  what  may  be  hereafter  discovered  in  relation 
to  the  action  of  this  system  that  our  chief  hopes  of  the  ad- 
vance of  animal  chemistry  and  physiology  depend. 

Of  what  are  bones  composed  ?  What  are  the  chief  constituents  of 
nervous  matter? 


INDEX. 


A. 

Acid,  glucic,  316.                            « 

Absolute  alcohol,  323. 

hippuric,  346. 

AcetaJ,  332. 

hydriodic,  236. 

Acetification,  332. 

hydrochloric,  231. 

Acetone,  335. 
Acetyle  compounds,  331. 
Acid,  acetic,  332. 

hydrocyanic,  351. 
hydroferrocyanic,  355 
hydrofluoric,  238. 

aconitic,  or  equisetic,  364. 

hydrofluosilicic,  248. 

aldehydic,  331. 
alloxanic,  360. 
amygdalinic,  353. 
anilic,  or  iudigotic,  374. 
anthranilic,  374. 

hydros  alicylic,  347. 
hydrosulphocyanit,  357 
hydrosulphunc,  220. 
hyperchloric,  230. 
hyperchlorous,  230. 

antimouic,  293. 

hypermanganic,  275. 

antimonious,  293. 

hyponitrous,  207. 

apocrenic,  384. 
arsenic,  292. 

hyposulphuric,  219. 
hyposulphurous,  219. 

arseuious,  288. 

igasuric,  370. 

tests.  for,  289. 

isatinic,  374. 

benzoic,  344. 

isethionic,  330. 

boracic,  246. 

japonic,  365. 

butyric,  3-21. 

kinic,  370. 

capric  and  caproic,  378. 

lactic,  324. 

carbolic,  382. 

lithic,  359. 

carbonic,  241. 

maleic,  365. 

liquefaction  of,  243. 

malic,  364. 

chloracetic,  334. 

manganic,  274. 

chloric,  230. 

margaric,  377. 

chlorous,  230. 

meconic,  369. 

chloro-valerisic,  343. 

melanic,  348. 

chromic,  286. 

melasinic,  316. 

chrysammic,  374. 

mesoxalic,  360. 

chrysaiiilic,  374. 
cinuamic,  349. 

inetagallic,  366. 
metaphosphoric,  225. 

citric,  364. 

mucic,  318. 

comenic,  369. 

muriatic,  231. 

crenic,  383. 

mykomelinic.  360; 

croconic,  318. 

myristic,  378. 

cyanic,  353. 

nitric,  209. 

cyanuric,  354. 

nitromuriatic,  234. 

dialuric,  361. 

nitrous,  208. 

elaidic,  378. 

oenanthic,  327. 

ellagic,  366. 

oleic,  377. 

ethalic,  378. 

oxalic,  316. 

ethionic,  330. 

oxalhydric,  318. 

ferric,  279. 

oxaluric,  360. 

formic,  340. 

palmitic,  378. 

fulnainic,  354. 

parabanic,  360. 

fumaric,  365. 

pectic,  314. 

gallic,  366. 

phosphoric,  224. 

L  L  2 

402 


INDEX. 


Acid    phosphorous,  224.        .  .• 
phosphovinic,  328. 
picric,  or  carbazotic,  374. 

pinic,  sylvic  and  pimaric, 

purpuric,  361. 

pyrogallic,  366. 

pyroligneous,  332. 

pyromeconic,  369. 

pyrophosphoric,  225. 

pyrotartaric,  363. 

racemic,  363. 

rhodizonic,  318. 

rubinic,  365. 

saccharic,  318. 

sacchulmic,  316. 

salicylic,  347. 

sebaoic,  378. 

silicic,  247." 

stearic,  377. 

suberic,  378. 

succinic,  378. 

sulphamilic,  343. 

sulphindigotic,  373. 

sulphobenzoic,  344. 

sulphoglyceric,  377. 

sulphomethylic,  340. 

sulphonaphthalic,  382. 

sulphosaccharic,  315. 

sulphovinic,  327. 

sulphuric,  217. 

sulphurous,  215. 

tannic,  365. 

tartaric,  362. 

thionuric,  360. 

ulmic,  316,  383. 

uramilic,  361. 

uric,  359. 

valerianic,  343. 

xanthic,  336. 
Acids,  coupled,  362. 
Aconitine,  370. 
Affinity,  chemical,  164. 
Albumen,  389-390. 

vegetable,  389. 
Alcargen,  338. 
Alcohol,  323. 
Aldehyde,  331. 
Alizarine,  372. 
Alkarsin,  337. 
Allantoin,  359. 
Alloxan,  359. 
Alloxantine,  361. 
Alumina,  271. 

sulphates,  273. 
Aluminum,  271. 
Alums,  273. 

Amalgamation  process,  299. 
Amalgams,  303. 
Amidine,  312. 
Amidogen,  249. 


380. 


Amilen,  343. 

Ammeline  and  ammelide,  357. 
Ammonia,  carbonate,  350. 
nitrate,  350. 

preparation  and  proper- 
ties of,  249,  349. 
sulphate,  350. 

Ammoniacal  amalgam,  250,  349. 
Ammonium,  250.  . 

chloride,  350. 
sulphurets,  251. 
Amygdaline,  352. 
Amyle  compounds,  342. 
Anatto,  372. 
Aniline,  367,  371,  373. 
Animal  chemistry,  384. 
Anthracite,  239. 
Antiarine,  370. 
Antimony,  292. 

chloride,  293. 
oxide,  293. 
sulphurets,  294. 
Aqua  regia,  234. 
Arabine,  314. 
Argol,  322. 
Aricine,  370. 
Arrow-root,  312. 
Arsenic,  287. 

sulphurets,  292. 
Arterialization,  396. 
Arterial  membrane,  391. 
Atmosphere,    composition  of,  191. 

physical   constitution 

of,  190. 

Atmospheric  pressure,  192. 
Atomic  weights,  145. 
Atoms,  5. 
Atropine,  370. 
Aurum  musivum,  285. 
Azote,  188. 


Balloons,  16. 

Balsams,  381. 

Barium,  264. 

chloride,  265 
oxides,  265. 
sulphuret,  265. 

Barley  sugar,  313. 

Barometer,  200. 

Baryta,  265. 

carbonate,  266, 
sulphate,  266. 

Bassorine,  314. 

Batteries,  voltaic,  120. 

Bell  metal,  296. 

Benzamide.  345. 

Benzine.  346. 

Benzoine,  345. 

Benzone,  346, 


INDEX. 


403 


Benzyle  compounds,  344. 
Bile,  398. 
Biscuit-ware,  272. 
Bismuth.  299. 

nitrates,  299. 

oxides,  299. 

Bleaching  powder,  269. 
Blood,  composition  of,  395* 
Boiling  points  of  fluids,  47. 
Bone  earth,  269. 
Bones,  composition  of,  399. 
Boron,  246. 

Brain,  composition  of,  398. 
Brass,  296. 
British  gum,  313.    - 
Bromine,  preparation  and  properties 

of,  237. 
Brucia,  370. 
Buffy  coat,  391. 
Butyrine,  378. 

C. 

Cadmium,  283. 

compounds  of,  283. 
Caffeine,  370. 
Calamine,  electric,  283. 
Calcium,  267. 

chloride,  268. 

fluoride,  268. 

sulphurets  of,  268. 
Calculi,  urinary,  398. 
Calomel,  302. 
Calorimeter,  29. 
Camphor,  379. 

artificial,  379. 
Caoutchouc,  380. 
Capacity  for  heat,  28. 
Caramel,  313. 
Carbon,  238. 

chlorides  of,  329. 

its  compounds  with  oxygen, 

240. 

sulphuret  of,  246. 
Carbonic    oxide,    preparation    and 

properties  of,  240. 
Carbyle,  sulphate  of,  330. 
Carmine,  374. 
Carthamine,  372. 
Caseine,  389-390. 

vegetable,  389. 
Cassava,  312. 
Cast  iron,  277. 
Catechin  and  catechu,  365. 
Cedriret,  382. 
Cellulose,  315. 
Cerine,  378. 
Cerium,  273. 

Chameleon,  mineral,  275. 
Charcoal,  properties  of,  239. 
Chinoidine,  370. 


Chloral,  335. 
Chloric  acid,  230. 
Chlorine,  226. 

compounds  with  oxygen, 

229. 
preparation  and  properties 

of,  227. 

Chlorisatine,  374. 
Chlorocinnose,  349. 
Chloroform,  341. 
Chlorophyle,  372. 
Chlorosamide,  348. 
Chlorureted  acetic  ether,  336. 

formic  ether,  336. 
Chlorous  acid,  230. 
Cholesterine,  378. 
Chondrine,  391. 
Chrome  yellow,  287. 
Chromic  acid,  salts  of,  287. 

oxide,  salts  of,  286. 
Chromium,  285. 

oxide,  285. 
Chyle,  386,  398. 
Chyme,  386. 
Cinchona,  369. 
Cinnabar,  303. 
Cinnamyle  compounds,  348. 
Circulation  of  blood,  392. 
Clays,  composition  of,  273. 
Clay  iron  stone,  276. 
Coagulation,  394. 
Coal,  384. 

oil,  382. 
Cobalt,  281. 

characters  of  salts  of,  281. 

chloride,  282. 

oxalate,  281. 

oxides,  281. 
Cobaltocyanogen,  357. 
Cocoa  tallow,  378. 
Codeine,  368. 
Cohesion,  7. 
Colchicine,  370. 
Cold  rays,  69. 
Colophony,  380. 
Coloring  principles,  371. 
Colors,  82. 
Columbium,  287. 
Combination,  by  volumes,  154. 

laws  of,  151. 
Combining  numbers,  153. 

table  of,  145. 
Combustion,  174. 
Compound  radicals,  309. 
Condensation  of  vapors,  45. 
Conicine,  or  conia,  370. 
Copper,  295. 

alloys  of,  296. 

arsenite,  296. 

carbonates,  296. 


404 


INDEX. 


Copper,  nitrate,  296. 
oxides,  295. 
sulphate,  296. 
Corrosive  sublimate,  303. 
Creasote,  381. 
Cryophorus,  50. 
Crystallization  ;  crystallography, 

156. 

Cupellation,  300. 
Curarine,  370. 
Cyamelide,  353. 
Cyanides,  metallic,  353. 
Cyanogen,  245,  350. 

chlorides  of,  355. 
Cystic  oxide,  361. 

D. 

Daguerreotype,  92. 
Dammar  resin,  380. 
Daphnine,  370, 
Daturine,  370. 

Decomposition  of  water,  124. 
Delphinine,  370. 
Deutoxide  of  nitrogen,  206. 
Dew,  69. 
Dew-point,  52. 
Dextrine,  312. 
Diamond,  239. 
Diastase,  312. 

Differential  thermometer,  17. 
Diffusion  of  gases,  202. 
Digestion,  386. 
Dimorphism,  160. 
Dispersion,  74. 
Dragon's  blood,  380. 
Dross,  297. 
Dutch  liquid,  329. 

E. 

Earthen-ware,  manufacture  of,  272. 
Ebullition,  44. 
Elaidine,  378. 
Elaldehyde,  331. 
Elaterine,  370. 

Electricity,  action  of,  on  the  magnet, 
133. 

animal,  142. 

conduction  of,  99. 

of  steam,  142. 

statical,  97. 

voltaic,  115. 
Electro-chemistry,  125. 
Electrolysis,  126. 
Electrometers,  112. 
Electrotype,  129. 
Electrophorus,  115. 
Emetine,  370. 
Emulsine,  352. 
Enamel,  284. 
Equivalent  numbers,  145. 


Equivalent  numbers,  table  of,  145. 
Eremaeausis,  310. 
Essences,  379. 
Ethal,  378. 
Ether,  324. 

continuous  process  for,  328. 
Ethers,  compound,  326. 
Ether,  heavy  muriatic,  335. 
Etherole  and  etherine,  330. 
Ethyle  group,  325. 
Eudiometer,  lire's,  190. 
Eupione,  381. 
Evaporation,  55. 

at  low  temperatures, 

56. 
Expansion  of  solids,  23. 

fluids,  18. 

gases,  15. 

F. 

Faraday's  theory  of  polarization,  113. 
Fatty  bodies,  375. 
Fermentation,  alcoholic,  320. 

lactic,  321,  324. 

Ferridcyanogen  compounds,  356. 
Ferrocyanogen  compounds,  355. 
Fibrine,  389. 

vegetable,  389. 
Fixed  air,  242. 
Flame,  structure  of,  176. 
Fluoride  of  boron,  247. 
Fluorine,  237. 
Formomethylal,  341. 
Freezing  of  water  by  evaporation, 

51. 

Freezing  mixtures,  37. 
Fusel  oil,  342. 
Fusible  metal,  299. 

G. 

Galvanism,  116. 
Galvanometer,  135. 
Gamboge,  372. 
Gay-Lussac's  law,  204. 
Gelatine,  391. 
Gentianine,  370. 
Geoffroy's  tables,  167. 
Glass,  manufacture  of,  273. 

soluble,  273. 
Globuline,  393. 
Glucinum,  273. 
Glucose,  313. 
Glycerine,  376,  377. 
Gold,  303. 

compounds  of,  304. 
Goniometers,  159. 
Goulard's  water,  334. 
Graphite,  239. 

Gravity,  specific,  of  gases,  determi- 
nation of,  155. 


INDEX. 


405 


Green,  Scheele's,  296. 
Grove's  battery,  122. 
Gum,  British,  313. 

Arabic — tragacanth,  314. 
Gun  cotton,  318. 
Gunpowder,  260 
Gypsum,  269. 

H. 

Hoemaphein,  393. 
Haematite,  276. 
Hair,  391. 
Hare's  batteries,  121-131. 

blow-pipe,  182. 
Heat,  animal,  396. 

capacity  for,  28. 
conduction  of,  56. 
exchanges  of,  67. 
latent,  36. 

radiation,   reflection,    absorp- 
tion, and  transmission  of,  63. 
varieties- of,  67. 
Hematine,  393. 
Hematoxyline,  372. 
Hesperidine,  370-.  "•'«„' 
ilorn,  391. 

Hydrobenz amide,  345. 
Hydrogen,   antimoniureted,  294. 
arseniureted,  292. 
light  carbureted,  243. 
peroxide  of,  188. 
persulphuret  of,  222. 
phosphureted,  226. 
preparation  and  proper- 
ties of,  178. 
sulphureted,  220. 
Hygrometer,  Daniell's,  52. 
Hygrometry,  51. 
Hyoscyamine,  370. 
Hyponitrous  acid,  207. 
Hyposulphurous  acid,  219. 

I. 

Ideal  coloration,  94. 
Idrialine,  384. 
Indigo,  373. 
Induction,  102. 
Interference,  83. 
Interstices,  6. 
Inuline,  312. 
Iodine,  preparation  and  properties 

of,  234. 
Indium,  306. 
Iron,  276. 

carbonate,  280 
cast,  varieties  of,  277. 
characters  of  salts  of,  278. 
chlorides,  280. 
manufacture,  276. 
oxides  of,  278. 
passive,  278. 


Iron,  sulphates,  280. 
sulphurets,  280. 
Isatine,  374. 
Isomerism,  162. 
Isomorphism,  161. 

K. 

Kakodyle  and  its  compounds,  327. 
Kapnomor,  382. 
Kermes  mineral,  294. 
Kyanol,  382. 

L. 

Lac,  380. 
Lactine,  314. 
Lampblack,  239. 
Lamps,  safety,  58. 
Lanthanium,  273.      ~_ 
Latent  heat,  36. 
Laughing  gas,  205. 
Laws  of  combination,  151. 
Lead,  297. 

action  of  water  on,  297. 

alloys  of,  299. 

carbonate,  298. 

characters  of  salts  of,  298 

chloride,  298. 

iodide,  298. 

nitrate,  299. 

oxides,  298. 
Leaven,  319. 
Lecanorine,  374. 
Leiocome,  313. 
Leukol,  371. 
Leyden  jars,  108. 
Light,  cause  of,  71. 

chemical  action  of,  77. 

reflection,  refraction,  and  po- 
larization of,  87-89. 

•wave  theory,  71,  78. 
Lignine,  315. 
Lignite,  383. 
Lime,  267. 

carbonate,  268. 

chloride,  269. 

phosphate,  269. 

salts,  characters  of,  268. 

sulphate,  269. 
Liquor  of  Libavius,  285. 
Lithium,  264. 
Litmus,  374. 

M. 

Madder,  372. 
Magnesia,  269. 

carbonate,  270. 
characters  of  salts  of,  270. 
phosphate,  271. 
sulphate,  270. 

Magnesium,  preparation  and  prop 
erties  of,  269. 


406 


INDEX, 


Magnetism,  134. 
Magnets,  artificial,  137. 
Magneto-electricity,  139. 
Malachite,  296.          .'  j,.' ., 
Manganese,  characters  of  salts  of, 

274. 

chloride,  275. 
oxides  of,  274. 
preparation   and  prop- 
erties of,  274. 
sulphate,  276. 
Margarine,  376,  377. 
Margarone,  377. 
Marriotte,  law  of,  43,  203. 
Marsh's  test  for  arsenic,  290. 
Maximum  density,  21. 
Meconine,  368-370. 
Medicated  waters,  379. 
Melam  and  melainine,  357. 
Mellon,  358. 
Mercaptan,  336. 
Mercury,  302. 

characters  of  salts  of,  303. 

chlorides,  302. 

iodides,  303. 

nitrates,  303. 

oxides  of,  302. 

sulphates,  303. 

sulphurets,  303. 
Mesityle,  335. 
Metaldehyde,  331. 
Metal,  fusible,  299. 
Metals,  general  properties  of,  252. 

classification  of,  253. 
Methyle  compounds,  338. 
Microcosmic  salt,  264. 
Milk,  composition  of,  397. 
Mindererus  spirit,  333. 
Mineral  chameleon,  275. 
Molybdenum,  287. 
Mordants,  272. 
Morphia,  368. 
Mosaic  gold,  285. 
Mucilage,  314. 
Mucus,  398. 
Multipliers,  135. 
Murexan,  361. 
Murexide,  361. 
Muscovado  sugar,  313. 
Myricine,  378. 

N. 

Naphtha,  382-384. 
Naphthaline;  382. 
Narceine,  368. 
Narcotine,  368. 
Nervous  substance,  399. 
Nickel,  281. 

sulphate,  281. 
Nihil  album,  282. 


Nitric  acid,  209. 
Nitrobenzide,  346. 
Nitrogen,  chloride  of,  231. 

its  compounds  with  oxy- 
gen, 189. 

preparations  and  proper- 
ties of,  188. 
Nitrous  acid,  208. 

oxide,  205. 
Nomenclature,  144. 
Nutmeg  butter,  378. 
Nutrition,  function  of,  392. 

O. 

GEnanthic  ether,  327. 
Ohm's  theory,  131. 
Oils  and  fats,  375. 
Oil  of  bitter  almonds,  344. 

cajeput,  379. 

cinnamon,  348. 

copaiba,  379. 

horseradish,  379. 

lavender,  379. 

lemons,  379. 

mustard,  379. 

peppermint,  379. 

rosemary,  379. 

spiraea,  347. 

storax.  379. 

turpentine,  379. 

vitriol,  preparation  of,  217 

wine,  heavy,  329. 
Oils,  palm  and  cocoa,  378. 

volatile,  378. 
Oleine,  376,  377. 
Olefiant  gas,  244. 
Orcine,  orceine,  374. 
Organic  bodies,  classification  of,  311. 
decomposition  of,  by 

heat,  308. 
general    characters 

of,  307. 

\  chemistry,  307. 

Orpiment,  292. 
Osmium,  287. 
Oxalates,  317. 
Oxamethane,  327. 
Oxamide,  318,  326. 
Oxygen,  preparation  and  properties 

of,  169. 
Ozokerite,  384. 

P. 

Palladium,  304. 
Palmitine,  378. 
Palm  oil,  378. 
Papin's  digester,  45. 
Paracyanogen,  351. 
Paraffine,  381. 
Paranaphthaline,  382. 


INDEX. 


407 


Paschal's  experiment,  201. 
Pectine,  314. 
Perchloric  acid,  230. 
Petroleum,  384. 
Pewter,  285. 
Phloridzine,  370. 
Phosphorescence,  78,  96. 
Phosphoric  acid,  224. 
Phosphorus,  compounds  with  oxy- 
gen, 223. 

preparation  and  proper- 
ties of,  222. 

Phosphureted  hydrogen,  226. 
Photography,  93. 
Picamar,  382. 
Picrotoxine,  370. 
Pile,  voltaic,  120. 
Piperine,  370. 
Pitch,  381. 
Pit-coal,  384. 
Pittakal,  382. 
Plasma,  393. 
Platinum,  304. 

black,  305. 
chlorides,  305. 
oxides,  305. 

power  of  determining  un- 
ion of  gases,  305. 
salts,  combustible,  371. 
spongy,  305. 

Plumbago,  or  graphite,  239. 
Polarization  of  light,  87. 
Populine,  370. 

Porcelain,  manufacture  of,  272. 
Potassium,  chloride  of,  259. 
iodide  of,  259. 
peroxide  of,  257. 
preparation  and  proper- 
ties of,  256. 
sulphurets  of,  259. 
Potash,  257. 

bicarbonate,  259. 
bisulphate,  259. 
carbonate,  259, 
chlorate,  260. 
hydrate  of,  257. 
nitrate,  260. 
salts,  test  for,  258. 
sulphate,  259. 

Potato  oil  and  its  compounds,  342. 
Prism,  74. 
Proteine,  391. 
Prussian  blue,  356. 
Pseudomorphine,  368. 
Purple  of  Cassius,  284-304. 
Pus,  398. 

Putty  powder,  284. 
Pyroacetic  spirit,  335. 
Pyrometer,  23. 

Daniell's,  27. 


Pyroxylic  spirit,  339. 

Q,. 

Quercitron  bark,  372. 
Quicksilver,  302. 
duina,  369. 
Quinoline,  371. 

B. 

Radiation,  63.    " 
Rays  of  the  sun,  chemical,  91. 
Realgar,  292. ' 
Reflection,-  law  of,  89. 
Refraction,  law  of,  7 4,  89» 
Resins,  380. 
Respiration,  176. 
Rhodium,  306. 

S. 

Sacchulmine,  316. 
Safety  jet,  Hemming's,  58. 
Safety  lamp,  58. 
Sago,  312. 
Salicine,  347,  370. 
Salicyle  compounds,  347. 
Scheele's  green,  296. 
Secretion,  395. 
Selenium,  222. 
Silicon,  247. 
Silver,  299. 

ammoniuret,  301. 
characters  of  salts  of,  300. 
chloride,  301. 
German,  281. 
iodide,  301. 
nitrate,  301. 
oxides,  300. 
sulphuret,  301. 
Smalt,  281. 

Soaps  ;  saponification,  376. 
Soda,  biborate,  264. 

bicarbonate,  263. 
carbonate,  262. 
hydrate  of,  261. 
nitrate,  263. 
phosphates  of,  263. 
sulphate,  263. 
Soda  water,  242. 
Sodium,  chloride,  261. 

preparation  and  propertied 

of,  260. 
Solanine,  370. 
Solder,  285. 
Specific  gravity,  155. 

heat,  28. 
Spectres,  96. 
Spectrum,  solar,  75-78 
Speculum  metal,  296. 
Spermaceti,  378. 
Spiraea  ulmaria,  oil  of,  347. 
Starch,  310. 


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